Question 1101926
There has to be a typo somewhere,
because the numbers in the problem
make the number of 15 cent stamps Floyd bought {{{150/61=2&28/61}}} ,
and it should be a whole number, like 2 or 3.
 
This is how you would solve it:
LET {{{x}}} be the number of 15 cent stamps Floyd bought.
Then,
{{{x+6}}}= number of 10 cent stamps Floyd bought, and
{{{3(x+6)}}}= number of 10 cent stamps Floyd bought.
Calculating prices in cents.
{{{15x+10(x+6)+12(3(x+6))=426}}}
{{{15x+10(x+6)+12(3x+18)=426}}}
{{{15x+10x+60+36x+216=426}}}
{{{61x+276=426}}}
{{{61x=426-276}}}
{{{61x=150}}}
There is no integer solution to that.
{{{x=150/61=2&28/61}}}