Jane made some orange juice. She gave 4/5 of it to Ken and had 6/7 litre of juice left. How many litres of orange juice did Jane make? Express your answer as a fraction in its simplest for.
6/7 × 5 = 4 2/7
I do not understand why since it make of 4 2/7 then gave away 4/5 and cannot get back juice left of 6/7.