Question 199652
Let's use variables in solving:  <ABC = x , < PQR = y

Since x and y are supplementary, x+y = 180 by the definition of supplementary angles.

Also, x is 11 times as large as y, so x = 11y.

Now we have 2 equations with 2 variables and can solve using a variety of methods for systems of equations (i.e. substitution, multiplication with addition, etc)

Plug in x=11y to  x+y=180, so 12y = 180, and y = 15. Using this, we find that x = 165.