Answer:
Lin should expect to sell 10 cups more
Explanation:
The line c = 2t − 89 relates the cups Lin expect to sale (c) with the high temperature of the day (t)
If high temperature on Saturday is t1, then high temperature on Sunday is (t1+5)
Cups sold on Saturday are: 2t1 − 89
Cups sold on Sunday are: 2(t1+5) − 89 = 2t1 + 10 - 89
Cups sold on Sunday - Cups sold on Saturday:
2t1 + 10 - 89 - (2t1 − 89) = 2t1 + 10 - 89 - 2t1 + 89 = 10