1. First you have to write the equation in slope intercept form. To do that, you must have y be alone on one side.
2. move the 3x to the right side with the 5 by subtracting 3x from both sides. Since 3x will cancel on the left, y will be left alone.
3. Now that you're in slope intercept form, you can find the slope easily. The slope will always be the number in front of x. In this case, the number in front of x is -3. Therefore, -3 is your slope!