Final answer:
The cost of one slice of pizza is $1.75, determined by solving the system of equations from the two purchases.
Step-by-step explanation:
Let's denote the cost of one bottle of water as W and the cost of one slice of pizza as P. From the first purchase, we have the equation:
5W + 8P = $20.25
From the second purchase, we have:
1W + 3P = $6.50
By subtracting the second equation from the first (multiplied by 5), we can eliminate W and solve for P:
(5W + 8P) - 5(1W + 3P) = $20.25 - 5($6.50)
5W + 8P - 5W - 15P = $20.25 - $32.50
-7P = -$12.25
P = $12.25 / 7
P = $1.75
Therefore, the cost of one slice of pizza is $1.75.