Using the distributive property , 4*9+4*7 or 36+28
Assuming that CB is tangent, this is just a right triangle with a hypotenuse of 20 and a side of 12 so by the Pythagorean Theorem:
20^2=12^2+x^2
400=144+x^2
x^2=400-144
x^2=256
x=16
If you use the first answer, the equation becomes 2x + 2y = 16. You could subtract this from equation Q to eliminate x.
The second answer makes equation P -2x - 2y = -16. You could add this to equation Q to eliminate x. You can use both of these methods to eliminate the x term, but if you can only choose one, you should choose the second option.
