b) 75 acres to square meter
Consider that 1 acre = 4046.86m^2:
[tex]75\text{acres}\cdot\frac{4046.86m^2}{1acre}=303514.5m^2[/tex]c) 4637 nm^3 to in^3
First, consider that:
1 nm = 10^-9 m
1 m = 39.3701 in
then, you have:
[tex]1nm\cdot\frac{1m}{10^9nm}\cdot\frac{39.3701in}{1m}=3.9\cdot10^{-8}in[/tex]by powering to 3, you obtain:
[tex]\begin{gathered} (1nm)^3=(3.9\cdot10^{-8}in)^3 \\ 1nm^3=6.1\cdot10^{-23}in^3 \end{gathered}[/tex]Then, for the given quantity, you obtain:
[tex]4637nm^3\cdot\frac{6.1\cdot10^{-23}in^3}{1nm^3}=2.8\cdot10^{-19}in^3[/tex]c) 71.63 g/cm^3 to mg/dm^3
In this case, use two conversion factor for mass and volume in the same procedure, as follow:
[tex]71.63\frac{g}{\operatorname{cm}^3}\cdot\frac{1000mg}{1g}\cdot\frac{1dm^3}{1000\operatorname{cm}^3}=71.63\frac{mg}{dm^3}[/tex]