Question 114226
Let's let H=cost of hamburger and F=cost of fries.
1.{{{4H+3F=5.15}}}
2.{{{3H+5F=5.10}}}
Let me use equation 1 to solve for H in terms of F and then substitute into equation 2.
1.{{{4H+3F=5.15}}}
{{{4H=5.15-3F}}}
{{{H=1.2875-0.75F}}}
Now substitute into 2.
2.{{{3H+5F=5.10}}}
{{{3(1.2875-0.75F)+5F=5.10}}}
{{{3(1.2875)-3(0.75F)+5F=5.10}}}
{{{3.8625-2.25F+5F=5.10}}}
{{{3.8625+2.75F=5.10}}}
{{{2.75F=1.2375}}}
{{{F=0.45}}}
Now that you have F, you can substitute into either equation to find H. 
2.{{{3H+5F=5.10}}}
{{{3H+5(0.45)=5.10}}}
{{{3H+2.25=5.10}}}
{{{3H=2.85}}}
{{{H=0.95}}}
Hamburgers cost $0.95 and french fries cost $0.45. 
One hamburger and one order of fries would cost $1.40.