Reason:
Replace p with 2 and evaluate.
[tex]p^3 = 2^3 = 2*2*2 = 8[/tex]
Think of a cube that is 2 units along each side. It's volume is 2*2*2 = 8 cubic units. Repeated multiplication can be shortened to using exponents.
Another example: [tex]7^4 = 7*7*7*7[/tex]