The sum of two numbers is 15. One of the

numbers is 12 times the other. Find the

bigger number.

The Sum of two number is 15: x + y = 15

One of the numbers is 12 times the other: x = 12y:

System of equations:

x + y = 15

x = 12y

Plug x = 12y into equation one (x + y = 15)

12y + y = 15

13y = 15

y = 15/3

y ≈ 1.15

Now we know x = 12y

x = 12 (15/13) = 180/13

x = 180/13

x ≈ 13.85

The biggest number is x = 180/13.