Monday's gas, $3.80 rounded to the nearest tenth of a dollar would be $3.80 (its already there)
Tuesday' gas, $3.85 rounded to the nearest tenth of a dollar would be $3.90
Hope this helps!! and if you ever need anything else just ask! :)
I hope this picture helps you. I think its the right answer. Please forgive me if it isnt.
Answer:
With base of 3: 
With base of 9: 
Step-by-step explanation:
Use 3 and 9 as the base of the power.

Answer:
Micheal sent 40 messages, Christine sent 20, and Dave sent 11.
Step-by-step explanation:
Christine, Dale, and Michael sent a total of 71 messages
C + D + M = 71
Dale sent 9 fewer messages than Christine
D = C - 9
Michael sent 2 times as many messages as Christine
M = 2C
Plug-in the numbers.
C + C - 9 + 2C = 71
4C - 9 = 71
4C = 80
C = 20
Now, plug in to other equations for other results.
D = (20) - 9
D = 11
M = 2(20)
M = 40
Micheal sent 40 messages, Christine sent 20, and Dave sent 11.
Verify?
40 + 20 + 11 = 71.