Using the angle pair relationship solve for x. then select the correct value of x from the box on the right and drag and drop that value into the matched box.

x must be 19

Step-by-step 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.