Rewrite the following as powers of the specified base. An example is shown below.

$\left. \begin{array}{l}{ y = 5 ^ { x } \text { using base } 2 }\\{ \operatorname { log } _ { 2 } y = x \operatorname { log } _ { 2 } 5 }\\{ y = 2 ^ { x \operatorname { log } _ { 2 } 5 } }\end{array} \right.$

1. $y = 3^x$ using base $5$

2. $y = 7^x$ using base $10$

3. $y = 2^x$ using base $e$

   Answer (c):

   ln(y) = x ln(2)
   y = e^{x ln(2)}