Answer:
x = 20
Explanation:
Based on the square indication at the corner of the angle, we can assume it's a right angle, so 90°. This means that x + 3x + 10 = 90. Solve it like any algebraic equation, isolating x. add x to 3x + 10, this would net you 4x + 10 = 90. Subtract 10 on both sides of the equation to further isolate x, meaning 4x = 80. Simplify this, dividing 4 on both sides, meaning x = 20.