each month Rohan spends all his income on rent, travel and other living expenses. 1/3 of his income is used for rent, 1/5 on travel and £420 on other living expenses ... work out his income each month
1/3 + 1/5 = 8/15 (amount spent on rent and travel) 1 - 8/15 = 7/15 (amount spent on living expenses) 420 ÷ 7/15 = 899.999... = £900
