Question

The sum of two numbers is 15. When one of these numbers is added to three times the other, the result is 27. What are the numbers?

Answer 1

Set up 2 equations:

X + y = 15

X + 3y = 27

Multiply the first equation by -3:

-3x -3y = -45

Add the 2nd equation to the third one:

-2x = -18

Divide both sides by -2:

X = 9

Boy solve for y using the first equation, replacing x with 9:

9 + y = 15

Subtract 9 from both sides:

Y = 6

The two numbers are 9 and 6