What is the sum or difference 6x^7+8x^7

14x^7

You add the coefficients (numbers to the left of the variable terms) to get 6+8 = 14 which is the coefficient of the final answer. The x^7 stays the same. It's like saying "we have 6 apples added to 8 apples, so there are 14 apples overall". Replace "apples" with "x^7" and it's the same idea.