From my research, the attached image supports the question. In paralleograms, adjacent angles should equate to 180 degrees. Given the two equations of the 2 angles, we can solve for the missing value of x. This is shown below:
37 + (7x + 3) = 180
7x = 180 - 37 - 3
7x = 140
x = 20
Therefore, x = 20.