28) (a⁷)³·a¹⁰ / a²⁸, a=2

1. Simplify the numerator: a²¹·a¹⁰ / a²⁸ = a³¹ / a²⁸.
2. Simplify using exponent rules: a³¹⁻²⁸ = a³.
3. Substitute a=2: 2³ = 8.