Question 221223
{{{125x+75y=9000}}}
{{{x+y=100}}} so we have to solve this system of equations
{{{x=100-y}}}
{{{125(100-y)+75y=9000}}}
{{{12500-125y+75y=9000}}}
{{{12500-50y=9000}}}
{{{-50y=9000-12500}}}
{{{-50y=-3500}}} divide both sides by -50
{{{y=70}}}
{{{x=100-70=30}}}
so we need 30 tons at $125/ton and 70 tons at $75/ton