He i need again im bad at math so what is 3(ab-c) when a=7' b=4' and c= -3

Aregression was run to determine if there is a relationship between hours of tv watched per day (x) and number of situps a person can do (y). the results of the regression were: y=ax+b a=-0.662 b=30.418 r2=0.703921 r=-0.839

In the diagram, the measure of angle 9 is 85° which angle must also measure 85°?

Measures of the angle of r, 31 s (x+4) t (3x+9)