The correct answer to the first task, is:
7(x-3) = 4(x + 5) ( im assuming x + 5 by the ordering of the numbers, and ive seen many people doing the same mistake.)
7x-21 = 4x + 20
7x-4x = 21+20
3x = 41
The answer is 41/3.
I found this quite ugly, so i will do it by multiplication as it is acctualy written, also.
7x - 21 = 20x
7x-20x = 21
-13x = 21
x = -21/13 which is just as ugly.
If i input a - however:
7x-21 = 4x-20
3x = 1
x = 1/3
Thats all the possible answers, (except by division).
The correct answer to the second task, is 14 - x. Because she was x years younger than 14.