To answer this, add all of those angles. A triangle’s angles equal to 180. Then, combine like terms and solve.
5x - 40 + 3x + 2x + 20 = 180
10x - 20 = 180
10x -20 + 20 = 180 + 20
10x = 200
10x / 10 = 200 / 10
x = 20
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