For the cost to throw the event, we have to add $100+$500, the decorations and the DJ and then we have to add the variable for people times 5 since it is 5 per person. $100+500 = $600 and 5* n (the variable for people in the question)
We are adding the two terms so the final equation will be equal to:
600+5n
for b), we have to use the variable n for tickets times the constant 6 since it costs 6 dollars per person to enter, and that will be equal to the revenue the student council earns or R.