Answer:
First, if we look at these angles, we can see that they are vertical.
Vertical angles are congruent(meaning they measure the same degrees).
So let's set up an equation where -2x - 6 is equal to 40°, because they are vertical angles.
-2x - 6 = 40°
Solve for x!
Get rid of constants by performing the inverse operation of subtraction which is addition(because 6 is negative).
Make sure to apply this to both sides!!
(Add 6 to both sides)
+6 +6
-2x = 46
Now, we isolate x by getting of x's co-efficient.
To do that, we also perform the inverse operations.
The inverse operation of multiplication is division (since -2 is being multiplied by x).
(Divide -2 from both sides)
÷ -2 ÷ -2
x = -23
Therefore, x measures -23°.