Question

Erin is 8 years younger than twice Paula’s age. The sum of their ages is 40. How old is Erin

Answer 1

You do the sum(40) subtracted by 8, the answer from that divided by 2 since Erin's two times younger.
40-8=32
32÷2=16
Then if you want to check it you do the opposite and get the same sum(40) so 16×2=32 and 32+8=40