The person who gets this is a lucky winner. 63 points.

Since these are supplementary angles (angles that add up to 180) it should be
x = 180 - (37 + 53)

Solving this would give you
x = 180 - (37 + 53)
x = 180 - 90
x = 90

You are making this all add up to 180 degrees and so far you have to angles one of 53 and the other is 37.
53+37 is is 90 and now the second step is subtracting 90 from 180 so 180-90 is 90. The angle you are missing, x is equal to 90.
I hope this helped:))