Question 139408
The time it takes one of the pipes to fill the tank: x hours


The time it takes the other pipe to fill the tank: x + 15 hours
 

The faster pipe can then fill {{{1/x}}} of the tank in 1 hour.


The slower pipe can fill {{{1/(x+15)}}} of the tank in 1 hour.


Together they can fill the tank in 10 hours, so they can fill {{{1/10}}} of the tank in 1 hour.


But they also can fill {{{(1/x)+(1/(x+15))}}} of the tank in 1 hour, so:


{{{(1/x)+(1/(x+15))=1/10}}}


So just solve for x to get the value for the large pipe and add 15 for the value for the smaller pipe.


<big><b>Hint:</big></b> Find a common denominator for the left side and then cross multiply.