There are 2 white buttons and x x\,x black buttons in a box.
2 buttons are taken from the box at random.
The probability that both buttons are black is 1522\displaystyle \frac{15}{22}2215.
Work out the value of xxx.
43 exam-style questions on CCEA GCSE Maths Probability Equation Questions. Each one has a worked solution and a mark scheme showing where the marks go.