A. 3j+5p=7.60; 1j+2p=2.90
B. (j, p) = (0.70, 1.10)
C. $1.80
A. The bill is calculated by adding the products of quantity and price.
... 3j + 5p = 7.60 . . . . . . first bill
... 1j + 2p = 2.90 . . . . . . second bill
B. It is convenient to use the second equation to write an expression for j, then substitute that into the first equation.
... j = 2.90 -2p
... 3(2.90 -2p) +5p = 7.60 . . . . . substitute for j
... 8.70 -p = 7.60 . . . . . . . . . . . . eliminate parentheses, collect terms
... 1.10 = p . . . . . . . . . . . . . . . . . . add p-7.60
... j = 2.90 -2·1.10 . . . . put the value for p into the expression for j
... j = 0.70
C. j + p = 0.70 + 1.10 = 1.80
The cost of a juice and pancake special is $1.80.
