Can someone please help me?!?

Which values for a and b will create infinitely many solutions for this system of equations? ax-y=8 2x+y=b

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

In the equations, a and b represent the price per night for a room in hotel a and hotel b, respectively, w weeks after september 1 last autumn. what was the price per night in hotel a when it was equal to the price per night in hotel b? a = 240 − 20w b = 320 − 30w