Answer: a. 5
Since the angle is right, we know it is equal to 90 degrees.
Using the information provided, we can set up an equation.
50 + 5x + 15 = 90
Simplifying the equation, we get:
5x + 65 = 90
Subtracting 65 from both sides, we get:
5x = 25
Dividing both sides by 5, we get:
x = 5