#### Answer

a) $19.61$ miles per hr
b) $38.18$ miles per hr
c) $39$ times faster
d) $23.8$ times faster

#### Work Step by Step

a) Subtract the faster speed with the slower speed. In this case, we subtract the speed of the quarter horse with the speed of a human human.
$= 47.5 - 27.89$
$= 19.61$ miles per hr
b) Subtract the faster speed with the slower speed. In this case, we subtract the speed of the greyhound by the speed of a spider.
$= 39.35 - 1.17$
$= 38.18$ miles per hr
c) Let $x =$ how many times faster the spider is. We multiply the speed of the garden snail by $x$.
$0.03x = 1.17$
$x = \frac{1.17}{0.03}$
$x = 39$ times faster
d) Let $x =$ how many times faster the human is. We multiply the speed of the spider by $x$.
$1.17x = 27.89$
$x = \frac{27.89}{1.17}$
$x = 23.8376...$ times faster
$x \approx 23.8$ times faster