Answer:
EF = 58
Step-by-step explanation:
Starting with the premise that
DF = DE + EF, then
9x - 39 = 47 + 3x + 10 ( subtract 3x from both sides )
6x - 39 = 57 ( add 39 to both sides )
6x = 96 ( divide both sides by 6 )
x = 16
Hence
EF = 3x + 10 = (3 × 16) + 10 = 48 + 10 = 58
