180-(60 + 70) = 50 degrees for the portion of Q inside Triangle PTQ
Since Q is along line PQR and the portion Q outside of PTQ is also 50 then
180 - (50 + 50) = 80 degrees for the portion of Q inside Triangle QSR
The sum of the angles in Triangle QSR must equal 180
180 - (80 + 30) = 70 degrees is the measure of R
Since Triangles PTQ and QSR meet at Q along line PQR'; then Q is comprised of three angles along the line that must total 180 they are
50 + 50 + 80
I hope this helps
