Answer:

Step-by-step explanation:

hope this helps you.
I have no idea I am only in Middle School
It is best to use mental math with some equations (5x5 or something that is easy enough that work does not have to be shown 10 dived by 5
The error is that both sides of the equation have a variable. So if you were to combine your like terms, then you'd leave one side without a number and if your teacher is saying there is a left over number then it will be 0