O is the midpoint so both sides FO and OG need to equal each other.
3x + 17 = 7x - 15
Subtract 3x from both sides:
17 = 4x -15
Add 15 to both sides:
32 = 4x
Divide both sides by 4:
x = 32/4
X = 8
Now you have the value of X, solve for the lengths:
FO = 3x +17 = 3(8) +17 = 24 +17 = 41
OG = 7x -15 = 7(8) -15 = 56-15 = 41
Total length would be 41 + 41 = 82
First you had to remove parenthesis first.

Multiply by the numbers.

Final answer 



Hope this helps!
And thank you for posting your question at here on brainly, and have a great day.
-Charlie
18/1
36/2
72/4
...and many more....
Answer:
21/42
Step-by-step explanation:
Hope this helps :)