Since consecutive angles of parallelograms are supplementary (they add the equal 180 degrees), you can set up the following equation to solve:
5x - 2 + 3x + 10 = 180
8x + 8 = 180
8x = 172
x = 21.5
Now let’s check our work:
5(21.5) - 2 + 3(21.5) + 10 = 180
107.5 - 2 + 64.5 + 10 = 180
180 = 180
The answer:
x = 21.5
Hope this helps.