At a business meeting, everyone shook hands with everyone else exactly once. If there were a total of 10 handshakes, how many people were at the meeting.

Step-by-step explanation:

For this exercise it is important to remember the multiplication of signs. Notice that:

In this case you have the following expression given in the exercise:

Then you can follow the steps shown below in order to solve it:

Step 1: You must solve the subtraction of the numbers 0,65 and 3,21. Then:

Step 2: Now you must find the product of the decimal numbers above. In order to do that you must multiply the numbers.

(As you can notice, both are negative, therefore you know that the product will be positive).

Then, you get that the result is the following: