If |a-b|=c ,what is the value of a?

Hiii,

This is a very simple problem if you grasp the modulus concept on GMAT.

The be low is my approcah for any modulus qtn in GMAT.

Modulus concept:
The meaning of |x-y| is "On the number line, the distance between X and +Y"
The meaning of |x+y| is "On the number line, the distance between X and -Y"
The meaning of |x| is "On the number line, the distance between X and 0".

On the # line, Left to 0 are all the -ve #s and right to 0 are all +ve #s

E.g:
|x-3|=2 ==> distand between x and 3 is 2
==> i can have a # 2 units away to the left of three and also to the right of 3 on the # line
==> x could be 1 (2 units aways from 3 to the left) or 5 (2 units aways from 3 to the right)

Original qtn:

if |a-b|=c ,what is the value of a?
1. b=2
2.c=7


qtn says, on the # line, the distance between a and B is c.
what is the value of a?

stmnt1:
b = 2
the distance between a and 2 is c.....no luck

stmnt2:
the distance between a and B is 7
==> i have a 7 units line connected between a and b
==> no fixed value for a and b as i can move this line along the #,line keeping the distance constant i.e.7
no luck..Not suff.

1&2 together:
the distance between a and 2 is 7
==> |a-2|=7
==> a could be 9 or -5
Not suff.

Hence Answer "E".

Regards,
Murali.

Kudos?