Answer
$4.5 \text{ gallons}$
Work Step by Step
The rate at which the camel can drink is
\begin{array}{l}\require{cancel}
\dfrac{15\text{ gallons}}{10\text{ minutes}}
\\\\=
1.5\text{ gallons/minute}
.\end{array}
Hence, in $3$ minutes, the amount of water the camel can drink is
\begin{array}{l}\require{cancel}
\dfrac{1.5 \text{ gallons}}{\text{minute}}\cdot3\text{ minutes}
\\\\=
\dfrac{1.5 \text{ gallons}}{\cancel{\text{minute}}}\cdot3\cancel{\text{minutes}}
\\\\=
4.5 \text{ gallons}
.\end{array}
