TeX source:

\left(\frac{40 \mathrm{~m}}{\mathrm{~s}}\right)\left(\frac{3.28 \mathrm{ft}}{\mathrm{m}}\right)\left(\frac{1 \mathrm{mi}}{5280 \mathrm{ft}}\right)\left(\frac{60 \mathrm{~s}}{\min }\right)\left(\frac{60 \mathrm{~min}}{1 \mathrm{~h}}\right)=89 \, \mathrm{mph}