Question

Solve the pair of linear (simultaneous) equations by the method of elimination by substitution:
8x + 5y = 9
3x + 2y = 4

Answer 1

8x + 5y = 9     ...(1)
3x + 2y = 4     ...(2)

8x + 5y = 9

8x = 9 − 5y

`x = (9 - 5y)/8`    ...(3)

3x + 2y =  4

Putting x = `(9 - 5y)/8`

`3x ((9 - 5y)/8)` + 2y = 4

`(27 - 15y) /8 + 2y = 4`

`(27 - 15y + 16y)/8 = 4`

`(27 + y)/8 = 4`

27 + y = 32

y = 32 − 27

y = 5

Putting y = 5 in questions (3)

`x = (9 - 5 xx 5)/8`

`x = (9 - 25) /8`

= `-16/8`

x = −2