Answer
Because $5 \times 4^2 = 5 \times 4 \times 4 = 80 $
But $(5\times4)^2 = (5 \times 4) \times (5\times 4) = 5 \times 5 \times 4 \times4 = 400$
Work Step by Step
Because $5 \times 4^2 = 5 \times 4 \times 4 = 80 $
But $(5\times4)^2 = (5 \times 4) \times (5\times 4) = 5 \times 5 \times 4 \times4 = 400$