Question

Sarah's age exceeds Vika’s age by 16 years. Four years ago, Sarah was twice as old as Vika was then. Find the present age of each.

Answer 1

4 years ago, the 16-year age difference was Vika's age.

Sarah is 36; Vika is 20.

Answer 2

x is sarah
y = vika

two equations:
x = y + 16
and
(x-4) = 2(y-4)
x - 4 = 2y - 8
x = 2y - 4

substitute this eqn into the top equation from before x = y + 16 for all x in it

2y - 4 = y + 16
y - 4 = 16
y = 20

find sarah using x = 2y - 4

x = 2(20) - 4
x = 40 - 4
x = 36

sarah is 36 years old and vika is 20 years old