Answer: x = 20
Step-by-step explanation: We can use the Segment Addition Postulate.
If N is between M and P, then MN + NP = MP.
So we have 2x + 7 + 13 = 3x.
Solving from here, first simplify the left side to get 2x + 20 = 3x.
Now subtract 2x from both sides ti get 20 = x.
So the value of x is 20.