The angle we want is QPR (bottom left), which is one of the base angles. The other base angle is QRP (bottom right). These two angles are equal because PQR is an isosceles triangle (PQ = RQ)
So if we can find angle QRP, then we have found angle QPR
Note how angle QRP and the 140 degree angle combine to form a straight 180 degree angle. Therefore these two angles add to 180 degrees
It would be the negative form of those bumbers and the non-negative form of those numbers. The absolute value applies to negative numbers the same. For example absolute value of -3 is 3.
