Answer:
x = 28
Step-by-step explanation:
AB= AC
∠B = ∠C {Angles opposite to equal sides are equal}
∠A + ∠B + ∠C = 180 {angle sum property}
3x + x + 20 + x + 20 = 180 {Combine like terms}
3x +x +x + 20 + 20 = 180
5x + 40 = 180 {subtract 40 from both sides}
5x = 180 - 40
5x = 140 {divide both sides by 5}
x = 140/5
x = 28
