Respuesta :

DE + EF = 4x+2

DE = x+7

EF = 7

Substitute these in

x + 7 + 7 = 4x + 2

x + 14 = 4x + 2

subtract x from both sides

14 = 3x + 2

subtract 2 from both sides

3x = 12

divide both sides by 3

x = 4

substitute this in to find the length of DE

DE = x + 7

(4) + 7 = 11

the answer is 11

From figure we can see that:

DE=DF -EF

x+7 = 4x+2-7

combining like terms

x+7=4x-5

subtract x on the right side from 4x

7=(4x-x) -5

7=3x-5

add 5 on the left side

7+5=3x

12=3x

divide both sides by 3

x=4

DE=x+7 =4+7

DE=11