On Sunday, Sheldon bought 2 1/2 kg of plant food. He used 1 2/3 kg on his strawberry plants and used 1/4 kg on his tomato plants. How many kilograms of plant food did Sheldon have left?
2 1/2-1 2/3 is the same thing as 2 3/6- 1 4/6. The total after the strawberries is 5/6 kg. Now we need to subtract: 5/6-1/4 which can be converted into 10/12-3/12 which equals 7/12 kg.