Write the prime factorization of each number using exponents:

56 = ?
68 = ?

Make a factoring tree: 56 is 7 x 8. You can break 8 down into three 2s, therefore, 8 is equal to 2^3. 7 is already prime, so the answer is 2^3 x 7.
Same thing for 68: factored = 2 x 34 = 2 x 2 x 17
2^2 x 17 is the answer.