Answer
Please see the work below.
Work Step by Step
We know that
(a) $20ft=20ft\times (\frac{1m}{3ft})=7m$
(b) $60miles=60miles\times(\frac{1Km}{0.6miles})\times (\frac{1000m}{1Km})=100000m$
(c) $60mph=(60mph)(\frac{1\frac{m}{s}}{2mph})=30\frac{m}{s}$
(d) $8in=(8in)(\frac{1cm}{\frac{1}{2}in})(\frac{10^{-2}m}{1cm})=0.2m$
