Question

the sum of two numbers is 13 and there difference is 5 what are the 2 numbers?

Answer 1

x + y = 13
x - y = 5

x = (13 - y)

(13-y) - y = 5

13 - 2y = 5
-2y = -8
y = 4

x - 4 = 5
x = 9

x=9, y = 4

Answer 2

x+y=13
x-y=5
we can addd these 2 equations to eliminate y

2x+0y=18
2x=18
divide both sides by 2
x=9

sub back
x+y=13
9+y=13
minus 9 both sides
y=4

the 2 numbers are 9 and 4