Solution:
Let d and p represent the costs of a drink and a pizza slice, respectively. The two orders have a value:
d + 3p = 8.50
2d + 2p = 8.00
Subtracting the second equation from twice the first gives;
2(d +3p) -(2d +2p) = 2(8.50) -(8.00)
this is equivalent to:
4p = 9.00
solving for p, we get:
p = 2.25
Solving the first equation for d and putting in the value, we have
d = 8.50 -3p = 8.50 -3·2.25 = 8.50 -6.75
that is:
d = 1.75
So that, we can conclude that the correct answer is:
System of linear equations:
d + 3p = 8.50
2d + 2p = 8.00
The solution to the system is:
The cost of a drink is $1.75; the cost of a pizza slice is $2.25.