Cody bought two burgers and two small fries for $14. Mary bought three burgers and four small fries for $23. How much does one burger cost?

B = cost of burger
f = cost of fries

2b + 2f = 14, so
b + f = 7
We’ll solve for f in terms of b:

f = 7-b

Then substitute that in to our other equation (what Marty bought) to get a numerical value for b:

3b + 4f = 23
3b + 4(7-b) = 23
3b + 28 -4b = 23
-b = -5
b = 5

Then calculate f:
f = 7-b
f = 7-5 = 2

Burger $5
Fries $2

Please lmk if you have questions.