Answer:
x = 8
EF = 20
DF = 29
ED = 20
Explanation:
In the triangle provided
m∠D = m∠F
That means it is an isosceles triangle and the sides DE and EF must be equal
So DE = EF
DE = 20, EF = 4x - 12
20 = 4x - 12
Switching sides:
4x - 12 = 20
Add 12 to both sides:
4x - 12 + 12 = 20 + 12
4x = 32
x = 32/4 = 8
EF = 4x - 12 = 4(8) - 12 = 20
(actually we don't need to calculate this since EF = DE = 20)
DF = 3x + 5 and with x = 8
DV = 3(8) + 5 = 29
ED is already given as 20 so I don't know why they are asking for it :)