Why does 5xy3
have a degree of 4?

The degree is 4 because the term shown has TWO variables, while y has an exponent of 3, x has an exponent of 1, add the exponents of the variables to find the degree

Hey there, 

Ok so we need to put this into slope-intercept form so we can find the slope eaisly, (y=mx+b) 

If we move x to the right side we are left with, 
2y=-x-3
Next we divide by 2 to free up the y, 

y=-1/2x-3/2, this is now in y=mx+b form. Making the slope -1/2

Hope this helped!