a.
If:
j - the price of a glass of juice
p - the price of a pancake special
Then:
3j + 5p = 7.60
j + 2p = 2.90
b.
If:
j + 2p = 2.90
Then:
j = 2.90 - 2p
We can substite j in the first equation.
If:
3j + 5p = 7.60
j = 2.90 - 2p
Then:
3×(2.90-2p) + 5p = 7.60
8.70 - 6p + 5p = 7.60
8.70 - p = 7.60
⇒ p = 8.70 - 7.60
⇒ p = 1.10
If:
j = 2.90 - 2p
p = 1.10
Then:
j = 2.90 - 2×1.10
j = 2.90 - 2.20
j = 0.70
Thus, the price of a glass of juice is $0.70 and the price of a pancake special is $1.10.
c.
If:
p = 1.10
j = 0.70
Then:
j + p = 1.10 + 0.70 = 1.80
Thus, the bill for 1 glass of orange juice and 1 pancake special is $1.80.