Christian is 3 times as old as Marie. Marie is 12 years younger than Christian. How old is Christian?

Answer 1

See second post.

Answer 2

Thank you! Appreciate your help. I needed something that is easy to understand and explain to a 5th grader.

Answer 3

Let c be Christian, and m be Marie. Then:
c=3m and
m=c-12
So:
3(c-12)=c
3c-36=c
2c=36
c=18
☺☺☺☺

Answer 4

Makes no sense. Where did 2c=36 come from?