If you take £28, what is 10% of 28? 2.8 So what is 30% of 28? You would do 2.8 x 3... which is? 8.4 And what is 5% of 28? You would half 2.8...so 1.4 Now add together 30% of 28 and 5% of 28... this gives 9.8 So finally take £9.80, which is 35% of £28, away from £28. What does this give? £18.20