As shown in the picture the entirety of DF is equal to 5x + 7. So, you have to find the value of x to find the answer. To do this set 5x + 7 even to 8 + 2x + 5 since that is just DF broken into two segments. Here’s my work:
8 + 2x + 5 = 5x + 7 5x + 7 = DF
6 = 3x 5(2) + 7 = DF
2 = x 10 + 7 = DF
17 = DF
