Answer:
A. 5
Step-by-step explanation:
Pre-Solving
We are given two angles that are across from each other. We know one is 78°, and the other is (12x + 18)°.
We want to find the value of x.
If two lines intersect, then the angles that are across from each other will be congruent. This is known as Vertical Angles Theorem.
Because of this, the angle that is 78° and the one that is (12x + 18)° will equal each other.
Solving
So, this means:
78 = 12x + 18
Subtract 18 from both sides.
78 = 12x + 18
-18 -18
_____________
60 = 12x
Divide both sides by 12.
60 = 12x
÷12 ÷12
___________
5 = x
x is equal to 5, so the answer is A.
