Question

Solve each pair of simultaneous equation only by substitution method
8x+3y=7
3x+5y= -9

Answer 1

x = 2, y = -3

8x + 3y = 7
3y = -8x + 7
y = -8/3x + 7/3

3x + 5y = -9
3x + 5(-8/3x + 7/3) = -9
3x - 40/3x + 35/3 = -9
9/3x - 40/3x + 35/3 = -27/3
-31/3x = -62/3
-31x = -62
x = 2

8(2) + 3y = 7
16 + 3y = 7
3y = -9
y = -3

Check
3(2) + 5(-3) = -9
6 - 15 = -9
-9 = -9 :)