Question 72214
<pre>
{{{ (4.2*10^(7+2n))/(2.1*10^(-8))=0.000002 }}}

Rewrite 0.000002  in scientific notation

       {{{2 * 10^-6}}}

Rewrite the whole equation again

{{{ (4.2*10^(7+2n))/(2.1*10^(-8))= 2*10^(-6)}}}

simplify the left side of the equation by dividing.

     {{{4.2/2.1 (10^7 + 2n + 8) = 2*10^(-6)}}}

              {{{ 2* 10^(2n+15) = 2*10^(-6)}}}

Since bases are the same,
          2n + 15 = -6
          2n = -6 - 15
          2n = -21
           n = -21/2 or -10.5