Adding exponents is something that is done when multiplying terms which contain exponents. If they have a common base like 3^5 x 3^6 (where ^ means "raised to the exponent of") you can simply add the exponents 5+6 together to get your final answer 3^11.
Suppose you want to add exponents, x^y+x^z
The answer is x^(y+z),
why? because x^y means x*x*x*x..... y times
x^z means x*x*x*x..... z time,
total you have to multiple x y+z time
so it is equal to x^(z+x)
