I don't understand how to do this

20 degrees

Step-by-step explanation:

You know that the three angles will add up to 180 degrees, so you can make an equation:

3x (angle 1) + 2x + 20 (angle 2) + 5x - 40 (angle 3) = 180

3x + 2x + 20 + 5x - 40 = 180

Then, solve

combine like terms

10x - 20 = 180

add 20 to both sides

10x = 200

divide both sides by 10

x = 20 degrees

the answer is a

step-by-step explanation:

because if you put 1 in to the square root of x it equals 300.

because linear equations are a lot simpler than quadratics equations, and linear equations formula is a lot easier to memorize. that's why i think they're harder.