Most likely, you are not following the proper order of operations as required in arithmetic. In an equation which involves addition (or subtraction) and multiplication (or division), you MUST do the multiplication and division FIRST, then you do the addition and subtraction. For example, in the equation:

2 + 6×3 – 10/5

You must do the multiplication and division first to get:

2 + 18 – 2

Then you can do the addition and subtraction to get 18.

If you were to do this problem and NOT follow the proper order of operations, here’s what would happen:

2 + 6×3 – 10/5

Addition

8×3 – 10/5

Multiplication

24 – 10/5

Subtraction

14/5

Division

And you would get the answer of 2.8, which is entirely wrong. This is why it is absolutely necessary to follow the order of operations.

Here’s another example equation. Suppose the temperature is 28° C:

v = 331.5 + 0.60xT

v = 331.5 + 0.60×28

the first thing you must do is 0.60×28, so that you get:

v = 331.5 + 16.8

Now you can add to get

348.3