Hello there!
When you multiply a negative number by a positive number, you will always end with a negative number. However, when you multiply them, you multiply them as you would with two positive numbers, but you'd switch it's value to negative.
For example;
-7 * 5
This is the same as multiplying 7 * 5, but you'd flip the value to negative.
-7 * 5 = -35
7 * 5 = 35
I hope you see the difference, and that my explanation was satisfactory enough and provided sufficient information for you to understand!