He can buy 2 bags of reindeer for $3.75 .The price for each bag will be
[tex]\begin{gathered} 2\text{ bag = \$3.75} \\ 1\text{ bag = ?} \\ \text{cross multiply} \\ \text{price per bag = }\frac{3.75}{2} \\ \text{price per bag = \$1.875} \end{gathered}[/tex]The number of full bag he can buy for $20 can be computed below
[tex]\begin{gathered} \text{ \$ 1.875 = 1 bag} \\ \text{ \$20 = ?} \\ \text{ number of bags = }\frac{20}{1.875} \\ \text{ number of bags = }10.6666666667 \\ \text{Number of full bag }=10 \end{gathered}[/tex]