Solve the Equation $$3 \mathrm { e } ^ { 2 \mathrm { x } } + 7 \mathrm { e } ^ { \mathrm { x } } = 20$$

Multiple Choice

Solve the equation. Give the answer in exact form.
- $$3 \mathrm { e } ^ { 2 \mathrm { x } } + 7 \mathrm { e } ^ { \mathrm { x } } = 20$$

A) $\left\{ \ln \frac { 3 } { 5 } \right\}$
B) $\left\{ \ln \frac { 5 } { 3 } \right\}$
C) $\left\{ \mathrm { e } ^ { 5 / 3 } , \mathrm { e } ^ { - 4 } \right\}$
D) $\left\{ \ln \frac { 5 } { 3 } , \ln ( - 4 ) \right\}$