Question

The sum of two numbers is seventy-two. Twice one of them equals ten times the other. What are the numbers?

Answer 1

the answer to the question is x=60

Answer 2

x+y=72
2x=10y

Solve one equation, then plug the answer into the other.

x=5y
5y+y=72
6y=72
y=12

Now that we have one answer, we can use that to solve the final answer.
x+y=72
x+12=72
x=60