Kenneth bought 15 chicken sandwiches and tuna sandwiches for $35.10. Each chicken sandwich costs $2.30 and each tuna sandwich costs $2.40. How many chicken sandwiches did Kenneth buy?
assumed all r tuna (15×$2.40-$35.10)÷($2.40-$2.30) = 9
Let C be the number of chiken sandwiches
Then 15 - C = the number of tuna sandwiches
We have
2.30C + 2.40 (15 - C) = 35.10 simplify
2.30C + 36 - 2.40C = 35.10
-10C = 35.10 - 36
-.10C = - .90
C = -.90 /-.10 = 9 chicken sandwiches
+80 
