Question

3x + 7x = ? explain your answer

Answer 1

I was just learning this! 
So basically since the variable is the same (x) all you want to do is add 3 with 7 to get 10, then add the x. So your answer would be
3x+7x = 10x

Answer 2

10x because since they both have an x you are able to add them together. hope this helped