Question: the line ab has equation 3x+5y=7?
Answer: The gradient of a line in the form y = ax + b, where a and b are some numbers, is the number a. So we need to get the equation 3x + 5y = 7 into the above form, with y on one side on its own! 5y = -3x + 7. y = (-3/5) x + (7/5).