Answer: Terms that have identical variable parts (same variable(s) and same exponent(s)). So in this case the like terms are -7q and 9q AND 2 and 6 are like terms *REMEMBER: constant (which are numbers with NO variables can also be like terms)
but to solve this:
first group the like terms so:
(-7q+9q) that gives us 2q
(2+6) that gives us 8
*In your FINAL answer ALWAYS put the number(s) with variables first so the final answer is 2q+8