2x + 5y = 7

2x - 3y = 15

1. 2x + 5y = 7

2. 3x + 6y = 3

Multiply Equation 1. by - 3 and Equation 2. by 2:

1'. - 6x - 15y = - 21

2'. 6x + 12y = 6

Add Equations 1' and 2' to eliminate x

y (-15 + 12) = (-21 + 6)

-3y = - 15

y = 5

Substitute this value of y into either Equation 1 or 2 and solve for x:

1. 2x + 5y = 7 ⇒ 2x + 5 (5) = 7

2x = (7 - 25) = - 18

x = - 9

Check answer:

Does 3 (-9) + 6 (5) = 3?

Does - 27 + 30 = 3?

YES!