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yashikaaggarwal
Angle DEC = 60
Angle DEA = 120 (180-DEC = supplementary angle)
Also CEF = 60+Y = Angle EBC + Angle ECB
60+Y = 60+EBC
EBC = Y
Hence we can say,
ED is parallel to BC (alternate angles)
Extend ED till it cut AB at H
Such that angle HEA = angle CED = 60° (opposite angle)
Now. AHE is an equilateral triangle too.
AE = ED
In triangle AED
Angle AED + EAD + EDA = 180
120 + 2EAD = 180
2EAD = 60
EAD = 30°

Draw an altitude EG such that it meet AD at G and
Extend EG such that it meet BC at I.
Now HBEI is a parallelogram, whose opposite angles are equal.
Also parallelogram diagonals bisect angle hence Angle HBE = angle IBE = 30° = Angle DEF = FEG.

In triangle FGE, angle EGF = 90° , angle GEF = 30° and
Remaining angle X = angle EFG = 180-90-30 = 60° .

Answer is D

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Hey yashikaaggarwal

can u please elaborate on above highlighted part :)
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yashikaaggarwal
Angle DEC = 60
Angle DEA = 120 (180-DEC = supplementary angle)
Also CEF = 60+Y = Angle EBC + Angle ECB
60+Y = 60+EBC
EBC = Y
Hence we can say,
ED is parallel to BC (alternate angles)
Extend ED till it cut AB at H
Such that angle HEA = angle CED = 60° (opposite angle)
Now. AHE is an equilateral triangle too.
AE = ED
In triangle AED
Angle AED + EAD + EDA = 180
120 + 2EAD = 180
2EAD = 60
EAD = 30°

Draw an altitude EG such that it meet AD at G and
Extend EG such that it meet BC at I.
Now HBEI is a parallelogram, whose opposite angles are equal.
Also parallelogram diagonals bisect angle hence Angle HBE = angle IBE = 30° = Angle DEF = FEG.

In triangle FGE, angle EGF = 90° , angle GEF = 30° and
Remaining angle X = angle EFG = 180-90-30 = 60° .

Answer is D

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Hey yashikaaggarwal

can u please elaborate on above highlighted part :)
See the diagram, AE is equal to ED by congruency of triangles AHE and CDE. I know the solution is way lengthy but I tried to put as many facts here without making it overbearing. every side has its own proving point, you might have to start from zero to get whole logic behind answer.
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MathRevolution
[GMAT math practice question]

\(△ABC\) and \(△CDE\) are equilateral triangles, as the figure shows. What is the measure of the \(∠x\)?

Attachment:
7.27PS.png

A. \(45°\)

B. \(50°\)

C. \(55°\)

D. \(60°\)

E. \(65°\)



Is there not an easy way.?
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Does anyone have an actually neat diagram or solution?
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=>

We have \(AC = BC, CD = CE\) and \(∠BCE = ∠DCE = 60°.\)

Triangles \(ACD\) and \(BCE\) are congruent.

Since \(∠EBC = ∠DAC\), we have \(∠x = ∠ACB = 60°.\)

Therefore, D is the correct answer.
Answer: D
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Take the case when AB=CE. In that case BE coincides with BA
Attachment:
Untitled.png
Untitled.png [ 5.81 KiB | Viewed 5719 times ]

x= 180-60-60 = 60
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MathRevolution
=>

We have \(AC = BC, CD = CE\) and \(∠BCE = ∠DCE = 60°.\)

Triangles \(ACD\) and \(BCE\) are congruent.

Since \(∠EBC = ∠DAC\), we have \(∠x = ∠ACB = 60°.\)

Therefore, D is the correct answer.
Answer: D

from where can you know that Triangle BCE is congruent with Triangle ACD? I can't figure this out.
Please help.
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