Answer
$x = 3$
Work Step by Step
We know that the three interior angles of a triangle equal $180^{\circ}$.
Let us set up the equation to add the three angles together. One angle measures $20x + 10$, the second measures $x - 20$, and the third measures $x + 25$:
$(20x + 10) + (30x - 2) + (7x + 1) = 180$
$20x + 10 + 30x - 2 + 7x + 1 = 180$
Group like terms on the left side of the equation:
$(20x + 30x + 7x) + (10 - 2 + 1) = 180$
Combine like terms:
$57x + 9 = 180$
Subtract $9$ from each side of the equation to isolate the $x$ term:
$57x + 9 - 9 = 180 - 9$
Subtract to simplify:
$57x = 171$
Divide both sides by $57$ to solve for $x$:
$x = 3$
