I think that she started with 10.. I'm not 100% sure, though
The third story, to get area you have to multiply length times width
The equation would be 4x+5y=6.33 and 3x+3y=4.11
so from their you would do the calculations and get 0.52 and 0.85
To make sure the caluclations aare right you just hae to put in the numbers for the x and y
4(0.52)+5(0.85)=6.33
So 1 donutis $).52
1 large coffee is $0.85