Story systems review

Question

Seven times a number plus three times another number equals negative one the sum of the two numbers is negative 3what are the two numbers

Answer 1

7x + 3y = -1

x + y = -3

multiplies the bottom equation by -3:

7x + 3y = -1

-3x + -3y = 9

Adds them together:

4x = 8

x=2

Per 2nd equation, y = -5