Question

If DF=9x-39, find EF

Answer 1

`EF = 58`

Explanation:

Given

`DF = 9x - 39`

`DE = 47`

`EF = 3x + 10`

See attachment

Required

Find
`EF`

Because E is a point between D and F, then:

`DF = DE + EF`

Substitute values for DF, DE and EF

`9x - 39 = 47 +3x + 10`

Collect Like Terms

`9x -3x = 47 +39 + 10`

`6x = 96`

Make x the subject

`x = (96)/(6)`

`x = 16`

Recall that:

`EF = 3x + 10`

Substitute 16 for x

`EF = 3 *16 + 10`

`EF = 48 + 10`

`EF = 58`