1. The problem states that Mila cuts a cake into 20 equal pieces and gives 16 pieces to Libby. 2. We need to find the fraction of the cake that Libby receives. 3. The fraction is the number of pieces Libby gets over the total number of pieces: $$\frac{16}{20}$$. 4. Simplify the fraction by dividing numerator and denominator by their greatest common divisor, which is 4: $$\frac{16 \div 4}{20 \div 4} = \frac{4}{5}$$. 5. Therefore, Libby gets $$\frac{4}{5}$$ of the cake.