When are you supposed to add the exponents of a base and when are you supposed to subtract them?  Watch this tutorial to find out.

Exponents should be added when multiplying bases that are the same.  Example: (a^3)(a^2) = a^3+2 = a ^5
 
Exponents should be added when dividing bases that are the same.  Example: b^5 / b^3 = b^5-3 = b^2