0.19 for one cookie and 0.59 for one doughnut
x for how much one cookie costs and y for how much one doughnut costs
6x+4y=3.5
12x+5y=5.23
solve by substitution: (elimination would work too)
4y=3.5-6x
y=0.875-1.5x
12x+5(0.875-1.5x)=5.23
12x+4.375x-7.5x=5.23
4.5x=0.855
x=0.19
now use x to solve for y:
6(0.19)+4y=3.5
1.14+4y=3.5
2.36=4y
y=0.59
Check the work: 6(0.19)+4(0.59)=3.5
