Write and solve (algebraically) an equation to find the value of x.
A-x = 84
B-x = 90
C-x = 29
D-x = 87

Answer: x = 29
Step-by-step explanation:
∠ABC and 87° are vertical angles, meaning they will be congruent. This means we can write and solve an equation to find the value of x. We will then isolate the variable by using the inverse operation of multiplication, which is division.
∠ABC = 87°
3x° = 87°
x = 29
C-x = 29