Question 16354
Like terms are any term that is EXACTLY ALIKE.
such as;
x+x=; you can add them together because they are exactly alike;
x+x=2x
But if you had terms such as;
{{{x+x^2}}}; you could not add them together because they are not exactly alike.
the first x is to the power of one, the second x is to the power of 2;
So in your equations;
8s - 3s + 4k =
You can subtract 8s-3s, because they are like terms;
8s-3s+4k=11s+4k; you can not add these together because they are not like terms, they have different variables. 
10x + 6y -5x =;
You can subtract 10x-5x, because they are like terms,
10x-5x=5x+6y; you can not add together because they are not like terms.
12 + 6p + 3q - 5p + 7q =
You can subtract 6p-5p=p;
3q+7q=10q;
So you have;
12+p+10q
You can not add the 12 because it is not like any other term.
Hope you understand
=)