All 4 diagonals that have O as the origin in the middle that are connected to a corner will be the same length. So, since OP is the same length as OL, you can make the equations equal each other and solve for x.
2x+5 = 3x+2
Move the 2 over to the left by subtracting it from both sides
2x + 3 = 3x
Move the 2x over to the right by subtracting it from both sides
3 = x