algebra 2 question from delta math

Question

The difference of the squares of two numbers is −20 . The sum of the numbers is 10 . Find the numbers. 

Answer 1

a + b = 10

a² - b² = -20

a² - b² = (a+b) (a-b) so that means - 20 = 10 (a-b) so a-b = -2

a+b = 10

a-b = -2

Add

2a = 8

a = 4

b = 6

6 + 4 = 10

And 4² - 6² = - 20

Answer 2

x+ y = 10

x-y =-20

2x =-10

x = -5

y = 15