Solve the pairs of simultaneous equations by the substitution method.

Question

5x-9y=17
3x-8y=5

Answer 1

(poor method for this particular question, but ...)

solve the second for x, (I look for the smallest coefficient)

3x = 5+8y
x = (5+8y)/3

sub into the first
5(5+8y)/3 - 9y = 17
multiply by 3 to eliminate fractions
5(5+8y) - 27y = 51
25 + 40y - 27y = 51
13y = 26
y = 2
then x = (5+16)/3 = 7

Answer 2

2x+4y=8
3x+4y=16

Answer 3

4x+7y=15
5x+9y=,19