Answer
\[ - 15{e^{ - 0.2x}} + C\]
Work Step by Step
\[\begin{gathered}
\int_{}^{} {3{e^{ - 0.2x}}dx} \hfill \\
\int_{}^{} {kg\,\left( x \right)dx = k\int_{}^{} {g\,\left( x \right)dx} } \hfill \\
3\int_{}^{} {{e^{ - 0.2x}}dx} \hfill \\
Use\,\,integral\,of\,\,\exp onential\,\,functions \hfill \\
\int_{}^{} {{e^{kx}}dx} = \frac{{{e^{kx}}}}{k} + C \hfill \\
Then \hfill \\
3\,\left( {\frac{{{e^{^{ - 0.2x}}}}}{{ - 0.2}}} \right) + C \hfill \\
Simplifying \hfill \\
3\,\left( { - 5{e^{ - 0.2x}}} \right) + C \hfill \\
- 15{e^{ - 0.2x}} + C \hfill \\
\end{gathered} \]