To paint a house, a painting company charges a flat rate of $500 for supplies plus $50 for each hour of labor. What is the slope of the line?

The slope of the line is 50. You can try looking at the equation, which is

y=50x+500

500 is your y-intercept, and is where the cost starts.

50 is your slope, since the cost goes up by $50 every time.

x is how many hours, which determines how many $50s there are.

I hope this helps. All in all, the slope is 50.