Answer:
<A = 117degrees
Step-by-step explanation:
<A and <B are verticle angles, as given. Hence they will be of equal measures. It is given that <A = 5x -3, and <B = 4x + 21.
Using this, set up an equation;
<A = <B
5x - 3 = 4x + 21
Inverse operations,
5x - 3 = 4x + 21
+3 +3
5x = 4x + 24
-4x -4x
x = 24
Now substitute back in, to find the measure of <A,
5x - 3
x = 24
5 ( 24 ) - 3
120 - 3
117
