Iām not exactly sure that my answer is accurate. However, when you are combining like terms you have to add the terms that are similar... hopefully that makes sense.
For example:
2x + 7 + 8x + 3
What you want to do is simply the expression
We can see that 2x and 8x are both coefficients
(A coefficient is a number that is going to be multiplied by a variable such as 3y, 2x, 7x and so on)
They are both like terms meaning that they can be combined
2x + 8x= 10x
Next, you want to see if you can combine anything else because our goal is to make the expression simplified.
7 and 3 can be combined because they are like terms
7+3= 10
Now that you have the new numbers I guess you can call it your answer should be
10x + 10
Hopefully this helps you answer the other questions. I did this lesson not too long ago so if you need help on anything else I can try to explain it.