There are 30 pens in a box. 12 of the pens are black. 7 of the pens are green. The rest of the pens are red. One of the pens is chosen at random.
Find the probability that the pen is red. Hence find the probability that the pen is not red.
236 exam-style questions on CCEA GCSE Maths Probability. Each one has a worked solution and a mark scheme showing where the marks go.