Question 707567
Allow 1, x
Allow 2, y


Accounting for the quantity of gold: 0.15x+0.40y=76.5 grams of Gold.  Note this uses both alloys available, as does the next equation;


Account for the quantity of lead:  0.25x+0.30y=116.5 grams Lead.


System to start with is this:
{{{0.15x+0.40y=76.5}}}
{{{0.25x+0.30y=116.5}}}


This will help to eliminate terms of y and to first solve for x.
3*({{{0.15x+0.40y=76.5}}})
4*({{{0.25x+0.30y=116.5}}})
Subtract one equation from the other.

  

....and THIS may help to eliminate terms of x and solve for y.
5*({{{0.15x+0.40y=76.5}}})
3*({{{0.25x+0.30y=116.5}}})
Subtract one equation from the other.