Bunuel wrote:

During a certain week, a seal ate 50 percent of the first 80 smelt it came across, and 30 percent of the remaining smelt it came across. If the seal ate 40 percent of the smelt it came across during the entire week, how many smelt did it eat?

A. 24

B. 32

C. 55

D. 64

E. 80

let x+40 be the total no of smelts

50% of the first 80 smelt = 40

remaining = x

30% of the remaining =0.3x

it ate 40% of the total

0.4(x+40)=40+0.3x

0.4x+16=40+0.3x

0.1x=24

x=240

total no of smelts = 280

it ate 40% of 280

=112

help me out here !!

Corrected above !!

let x+40 be the total no of smelts

50% of the first 80 smelt = 40

remaining would be (x+40)-80=x-40

so the equation becomes

0.4(x+40)=40+0.3(x-40)

0.4x+16=40+0.3x-12

x=120

total no of smelts =120+40=160

it ate 40% of 160 = 64

D