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.
