Question

DF= 78, DE = 5x -9, EF = 2x + 10, find DE.

Answer 1

DF = 78, DE = 5x - 9, EF = 2x + 10, find DE.

Solve for x first.

5x - 9 + 2x + 10 = 78

7x + 1 = 78

7x = 78 - 1

7x = 77/7

x = 11

Then substitute the value of x to find DE.

DE = 5x - 9

5(11) - 9

55 - 9

DE = 46

Therefore, the value of DE is 46

Answer 2

Question:

DF= 78, DE = 5x -9, EF = 2x + 10, find DE.

Solution:

First, solve for the value of x.

• DE + EF = DF
• (5x - 9) + (2x + 10) = 78
• 7x + 1 = 78
• 7x = 78 - 1
• 7x = 77/7
• x = 11

Then, plug and substitute the value of x to find the DE.

• DE
• 5x - 9
• 5(11) - 9
• 55 - 9
• 46

Answer:

• The value of DE is 46