If 5x + 3y = 14 and 3x + 5y = 18 then x + y = ----------. *

Answer 1

add the two equations and you have
8x+8y = 32
x+y = 4

Answer 2

5x + 3y = 14
Multiply both sides by 3
15x + 9y = 42

3x + 5y = 18
Multiply both sides by 5
15x + 25y = 90

15x + 25y = 90
-
15x + 9y = 42
_____________
16y = 48

y = 48 / 16 = 3

Put this value in equation:
5x + 3y = 14
5x + 3•3 = 14
5x + 9 = 14
Subtract 9 to both sides
5x = 5
x = 5 / 5 = 1

x + y = 1 + 3 = 4