Nicole did a terrific job of describing how you multiply a fraction and a whole number. :-) I only have one comment to add.
ANY number or variable multiplied by 1 is itself. That is true regardless of what kind of number it is. so, using a * to mean multiplication (that's what computers use) :
5 * 1 = 5
1/2 * 1 = 1/2
99/852 * 1 = 99/852
Q * 1 = Q
(orangutan) * 1 = (orangutan) ... and so on.
So if you are multiplying a fraction ... by one... you do not have to go through the multiplication process, you just know it is itself. In your example, (3/2)(1) simply is 3/2... then you subtract 3 from that. Nicole has explained the fraction and negative number math beautifully.