I need help solving this word problem..

Q1 )There was a need for one table at the catering company's first event. Two table were needed for the second event, three table the third event and so on. one table seats 10 and two table seats 18. If the table are always set up end to end and a total of 74, 800 guests have attended the company's events, how many events has the catering company handled? (Assume every seat has been filled at each even)...