Angles ABC and GFH are a pair of alternate exterior angles of these two parallel lines cut by a transversal. This means they are congruent (properties of two parallel lines cut by a transversal).
Set them equal to each other to find x.
10x + 20 = 12x
Subtract 10x from both sides.
20 = 2x
Divide both sides by 2.
10 = x
To find the measures of angles ABC and GFH, substitute 10 for x in their angle values accordingly and solve.
10x + 20
10(10) + 20
100 + 20
120
12x
12(10)
120
Answer:
x = 10; m∠ABC = 120; m∠GFH = 120
