Answer:
x must be 19
Explanation:
The sum of the four angles shown above the horizontal axis MUST be 180 degrees.
Thus we set up and solve the following equation:
5x + 4 + x - 2 + 3x + 7 = 180
Combining like terms, we get:
9x + 9 = 180
Dividing all three terms by 9 yields x + 1 = 20
From this we see that x must be 19.