Question

At a bake sale, a student spent $5.70 buying 3 brownies and 5 cookies. His

friend spent $4.50 buying 1 brownie and 6 cookies. What is the price of a
brownie?

Answer 1

$0.90, so 90 cents. Cookies are $0.60, 60 cents.

Answer 2

i think the answer would be 90 cents for each brownie

Explanation:

This can be solved as a system of 2 linear equations.

x = price of a brownie

y = price of a cookie

Since $5.70 bought 3 brownies and 5 cookies, our first equation is:

3x + 5y = 5.70

Since $4.50 bought 1 brownie and 6 cookies, our second equation is:

x + 6y = 4.50

So just solve the following system for x and y:

3x + 5y = 5.7

x + 6y = 4.5

Get x = 4.5 - 6y from the bottom equation and substitute for x in the top equation:

3(4.5 - 6y) + 5y = 5.7

Solve for y:

13.5 - 18y + 5y = 5.7

-13y = -7.8

y = 7.8/13 = 0.6 = price of cookie = $0.60

Now substitute this value of y into either equation and get x. From the bottom equation,

x + 6(0.60) = 4.50

Solve for x:

x = 0.9 = price of brownie = $0.90