GEOMETRY: Parallel and Perpendicular Lines Slope

*question is in the picture*

Amerchant has coffee worth $60 a pound that she wishes to mix with 50 pounds of coffee worth $90 a pound to get a mixture that she will sell for $70 a pound. how many pounds of the & 60 coffee should be used?

If sec theta = 5/3 and the terminal point determined by theta is in quadrant 4, then

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15