HELPP PLEASE !!! with number 21

I didn’t answer c or d I just need help with those please

Which expression will have the same sum as 3_8 + 1/4?

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?  

What is the slope of the line shown below?