Answer:
- granola bar: $1.50
- yogurt: $0.50
Step-by-step explanation:
You want the cost of each item when person A buys 10 granola bars and 6 cups of yogurt for $18, and person B buys 5 granola bars and 4 cups of yogurt for $9.50.
Equations
The equations describing the relations can be written ...
10g +6y = 18 . . . . . . . person A's purchase
5g +4y = 9.50 . . . . . . person B's purchase
Solution
Subtracting half of the first equation from the second, we find ...
(5g +4y) -1/2(10g +6y) = (9.50) -1/2(18)
y = 0.50 . . . . . . . . . . simplify
Substituting this into the first equation gives ...
10g +6(0.50) = 18
10g = 15 . . . . . . . . . . subtract 3
g = 1.50 . . . . . . . . . divide by 10
Each granola bar costs $1.50; each cup of yogurt costs $0.50.
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Additional comment
The attachment shows the solution found using a calculator to find the reduced row-echelon form of the augmented coefficient matrix. The variable values are in the right column of the reduced matrix. This tells us granola bars are $1.50, and yogurt cups are $0.50, as we found above.
