Write a segment addition problem using three points that asks the student to solve for x but has a solution x = 20

Let me give you an example of a segment addition problem that uses three points that asks the student to solve for x but has a solution x = 20.

First, I assumed values for each x, y and z and then manipulated their coefficients to get the total at the end of each equation.
20 + 10 +30 = 60
40 + 0 + 40 = 80
40 + 10 = 50

Then exchangeing these numbers into values and we have the following equation.
x + 2y + 3z = 60
2x + 4z = 80
2x + z = 50

If you will solve them manually by substituting their variables into these equations, you can get
x = 20
y = 5
z = 10