Question

I need help finding EF.

Answer 1

EF=40

Explanation:

DC=9, AB=x+11, EF=?

EF=x-20

EF=(AB+DC)/2

x-20=(x+11+9)/2

x-20=(x+20)/2

x-20=x/2+10

x-x/2=10+20

2x/2-x/2=30

x/2=30

x=30*2

x=60

EF=x-20=60-20=40