Answer
40.2 mph
Work Step by Step
Write a proportion. Mph decrease is to mph decrease as time is to time.
$\frac{3}{x}=\frac{5}{8}$ $\longrightarrow$cross multiply to solve for x
$5x=3\times8$ $\longrightarrow$multiply
$5x=24$ $\longrightarrow$multiplication property of equality
$5x\div5=24\div5$ $\longrightarrow$divide
$x=4.8$
New speed is $45-4.8=40.2$
