Help me find the value of x

We know that the entire angle is equal to 90 degrees (look at image below). This means that the sum of 4x-10 and x is 90 degrees, so you can make a formula:
4x - 10 + x = 90
Now you can solve for x
5x - 10 = 90
5x = 100
x = 20
Hope this helped!
Answer:
A) x = 20
Step-by-step explanation:
The horizontal line is a straight angle, so it is 180°, and the angles on the left is right, so it is 90°.
180 - 90 = 90, which means the two smaller angles total up to 90°.
So, 90 = 4x - 10 + x
Simplify: 90 = 5x - 10
Add: 100 = 5x
Divide: x = 20