The characteristics of a triangle require that pr be between what 2 values when pq =12 and rq=19

When 2 triangle sides are known
The third side must be less than the sum of the other 2 sides and
the third side must be greater then the difference of the other 2 sides.

Sum of the 2 sides = 31
Difference of the other 2 sides = 7

So, the third side must be greater than 7 and less than 31

Source:
http://www.1728.org/trianinq.htm

There is no graph but what i can say is that 1 is the slope and that -2 is the y- intercept