Firstly, you should change the equation into the form y=mx+c where m is the gradient and c is the y-intercept. This can be done by subtracting 3x from each side of the equation to give 5y=-3x+7. Then dividing each side of the equation to give y=-3/5x+7/5. By comparing this with the general equation y=mx+c, you can see that m= the gradient= -3/5.