What is the slope and the y-intercept?

To do this you want to isolate the y value. First, add 5x to both sides, so that it becomes 3y = -9 + 5x. Then, divide both sides by 3. You get -3+5x/3, which is equal to
Y=5x/3 -3 so the y intercept (where x is zero) would be -3, and the slope is 5/3

Change to slope intercept form.

Add 5x to both sides.

-5x + 5x + 3y = -9 + 5x

3y = 5x - 9

Now divide by 3.

y = 5/3x - 3

Remember that slope intercept is in the format y = mx + b 
m = slope
b = y-intercept

Good luck, that should do you good :)

Cthe residual plot for model 1 has a non random pattern and is a good fit for the data