What’s the equation?

The lines shown below are parallel. if the green line has a slope of -1, what is the slope of the red line?

If the ratio of sum of the first m and n terms of an ap is m2 : n2 , show that the ratio of its mth and nth terms is (2m − 1) : (2n − 1).

Ntriangle abc, m∠a = 35° and m∠b = 40°, and a=9. which equation should you solve to find b?