Answer:
45°
Step-by-step explanation:
The angle with measure of 9x and the angle with measure of 3x are supplementary
9x + 3x = 180°
12x = 180 divide both sides by 12
x = 15
The angle with measure of 9x and angle a are supplementary as well
9x + a = 180
9×15 + a = 180
135 + a = 180 subtract 135 ftom both sides
a = 45°
Short answer: (-8)^2 + 8 x -8 =
0
Use PEMDAS
"Evaluate the expression" just means solve until you can't simplify anymore. You must solve it in a certain order according to
PEMDAS: Parentheses, Exponents, Multiply, Divide, Add, Subtract.
What does the beginning of the expression look like? It is

.
According to PEMDAS, you must solve what is in the parentheses *first*. But, since there is only a number (-8), there is nothing to solve for and you can move on to exponents.
The squared symbol, the little 2, means you have to square what is *inside* the parentheses.

= 64, because -8 times itself is 64.
Next comes multiplication. Remember, we are not working from left to right. We must multiply the values on the far right before we do any adding, because multiplication comes *before* addition.
(64) + (8 times -8)
(64) + (-64)
Finally, we can add. In this case, because we are adding a negative number, we are really subtracting. 64 + -64 equals 0.