Answer:
$0.90
Step-by-step explanation:
Given tea is 10 cents less, and chocolate is 20 cents more than a cup of coffee, you want to know the price of a cup of coffee when 5 teas, 3 coffees, and 2 chocolates cost $8.90.
Let c represent the cost of a cup of coffee (in cents). Then tea is (c-10) and chocolate is (c+20). The total purchase is ...
5(c -10) +3c +2(c +20) = 890 . . . . . . . cents
Simplifying the equation, we have ...
10c -10 = 890
c -1 = 89 . . . . . . divide by 10
c = 90 . . . . . . . add 1
The price of a cup of coffee is $0.90.