Siobhan wrote an exam which had 18 questions. Each question she answers correctly gets her 10 marks. However, she loses 5 marks for each question she answers incorrectly. She attempted all the questions and got a total of 75 marks. How many questions did she answer wrong?
225 cola cans and 360 fruit juice cans need to be stacked in a school canteen. If each stack is to be of the same height and has to contain cans of the same type, find the greatest number of cans each stack can have.