Evaluating $3^{a-1}$

Question

If $$3^{-a}=2$$ Evaluate $$3^{a-1} $$

Here's my attempt:

$$3^{-a}=2$$

Rewriting the equation

$$3^{a}=2^{-1} \implies 3^{a-1} = 2^{-2} = \dfrac 1 4$$

Regards!

Answer 1

Not quite

If $3^{a}=2^{-1}$

then you need to divide both sides by $3$

to get $3^{a-1}$ on the left hand side

and the answer on the right hand side

Answer 2

You were almost there $$3^{a}=2^{-1} \implies 3^{a-1} = 2^{-2} = \dfrac 1 4$$ note that $$3^{a-1}=3^a \times 3^{-1}= \frac {3^a}3= {3^a}\times \frac 13$$ So multiply both side by 1/3