Question 67510
We have {{{1/4}}} + {{{1/5}}} = {{{1/x}}}
First, let's find the common denominator of {{{1/4}}} and {{{1/5}}} and add them.

We know both 4 and 5 will multiply into 20, so let's 20 as our common denominator.

{{{1/4}}} + {{{1/5}}} = {{{5/20}}} + {{{4/20}}} = {{{9/20}}}

So now we have,
{{{9/20}}} = {{{1/x}}}  First let's multiply both sides by x
{{{9/20}}}x = {{{1/x}}}*x
{{{9/20}}}x = 1  (Now divide both sides by {{{9/20}}})
{{{(9/20)/(9/20)}}}x = {{{1/(9/20)}}}
x = {{{1/(9/20)}}} = {{{20/9}}} 

Hope this helps you!!