Please help me with these questions and show how u got them, i will mark you brainliest !

Two lines parallel to a third line are parallel to each other. always sometimes or never

Aschool puts on a play. the play costs $1,200 in expenses. the students charge $4.00 for tickets. there will be one performance of the play in an auditorium that seats 500 people. what is the domain of the function that shows the profit as a function of the number of tickets sold?  

The ratios 3: 9, 4: 12, 5: 15, and 6: 18 are a pattern of equivalent ratios in the ratio table. which is another ratio in this pattern?