Answer:
r=7
Step-by-step explanation:
6r-7+90+55=180
6r+138=180 ----- 6r=180-138
6r=42 ----- divide both sides by 6
r=7
(We get the 90 from the 90degrees in the middle of this supplementary angle and the total, 180, from the straight angle made from all three angles.)
hope this helps!
