Question

Solve the pair of linear (simultaneous) equation by the method of elimination by substitution:
2x + 7y = 39
3x + 5y = 31

Answer 1

2x + 7y = 39                           ...(1)
3x + 5y = 31                           ...(2)

2x + 7y = 39
∴ x = `[39 - 7y]/2`

Putting this value of x in (2)
`3([ 39 - 7y]/2) + 5y = 31`

`117 - 21y + 10y = 62`

`- 11y = - 55`

`y = 5`

From (1) x = `[39 - 7(5)]/2`

x = `4/2`
x = 2