9514 1404 393
Answer:
42°
Step-by-step explanation:
The exterior angle of a triangle is equal to the sum of the remote interior angles.
Angle y exterior to ΔQSR is ...
y = x +21°
Angle 2y exterior to ΔQPR is ...
2y = 2x +∠QPR
Solving for ∠QPR, we have ...
∠QPR = 2(y -x) . . . . . subtract 2x from the second equation
Comparing to the first equation, we find ...
21° = y -x . . . . . . . . . . subtract x from the first equation
Substituting for y-x, we get ...
∠QPR = 2(21°) = 42°
