Solve: 9less than and equal to 3t+3less than and equal to 18?

Question

The answer is [2,5] but how do you get that answer?????

Answer 1

9<=3t+3<=18
subtract 3
6<=3t<=15
divide by 3
2<=t<=5
therefore [2,5]

Answer 2

First, trade in the verbige for symbols.
9 =< (3t+3) <= 18
Find the domain of t.
At one extreme, dropping the "<", 9=3t+3 or t=2
at the other, 3t+3=18, or t=5. So the domain of t is from 2 to 5.