Estimate the solution to each of these equations without a calculator and justify your estimate.  

1. $20^x=316$

   Hint (a):

   Since $20^2=400$, $x$ must be less than $2$.

2. $7.3^x=4.81$

   Hint (b):

   $7.3^1=7.3$, so $x$ must be less than $1$.

3. $160(0.5)^x=8$

   Step (c):

   $\left(\frac{1}{2}\right)^x=\frac{8}{160}=\frac{1}{20}$

   More Help (c):

   $\left(\frac{1}{2}\right)^4=\frac{1}{16}$