Answer
$5\times 4 \times 2 = 40$
Work Step by Step
$a \times b \times c =$ General formula for the answer
1. Multiply the first two numbers together ($a \times b$)
$5\times 4 = 20$
2. Multiply the previous number in #1 with the last number
$((a \times b) \times c)$
$20 \times 2 = 40$
