Question

How do you solve the system `c = 3d - 27` and `4d + 10c = 120` by substitution?

Answer 1

equations provided are:
`c = 3d -27` .................`(1)`
`4d +10c = 120` ..........`(2)`

Substituting equation `(1)` in equation `(2)`
`4d +10(3d -27) = 120`
`4d + 30d -270 = 120`
`34d = 390`
`d= (390/34) approx 11.5`

Substituting the value of `d` to find `c`

`c = 3d -27 = 3 xx (11.5)-27`
`=34.5-27 = 7.5`