Find X (I’m not the best with math!)

What is the solution to the system of the equations? x = y - 3 x + 3y = 13

Starting at home, emily traveled uphill to the hardware store for 606060 minutes at just 666 mph. she then traveled back home along the same path downhill at a speed of 121212 mph. what is her average speed for the entire trip from home to the hardware store and back?

If f(x) = 4x - 3 and g(x) = x + 4, find (f - g) (x)