Parallelogram: a four-sided figure with two sets of equal sides and two sets of equal angles. Angles opposite each other in a parallelogram are equal in measure. Sides opposite each other are also equal in length in this shape.
Therefore, we know that because this is a parallelogram, sides OL and NM will be equal in length. So, we can set the two equations equal to each other.
NM=x+23
OL=5x+7
NM=OL
x+23= 5x+7
23=4x+7
16=4x
4=x
Answer: x=4. Let me know if you have any further questions!