When dealing with expressions that have more than one operation, we follow something called the order of operation. Each operator has precedence. Some operators are more "significant" than others. Below will show each operator's precedence.
exponents
multiplication, division
addition, subtraction
Operations that are the same line are equal. But when solving the expression, you go left to right.
Now let's solve that expression!
3 * 18 - 12 + 14 * 2
What do we do first? Well will do the multiplication first. Because they have the precedence right now.
3 * 18 - 12 + 14 * 2 = 54 - 12 + 14 * 2
Now we have 54 - 12 + 14 * 2
Next we do the 14 * 2 part.
54 - 12 + 14 * 2 = 54 - 12 + 28
Now there are only addition and subtraction operators here. What do we do now? Addition and subtraction are both equal. We fix this by solving left to right.
So, the 54 - 12 is going to be solved first.
54 - 12 + 28 = 42 + 28
And finally
42 + 28 = 70