Level 3
Irene has enough flour to bake either 21a tarts or 18 biscuits. If she has finished baking 5a tarts and 6 biscuits, how many more tarts can she still bake in terms of a?
Level 2
A mini-bus can take either 12 adults or 15 children. There are 6 mini-buses altogether and there are 8 adults in each of the mini-buses. What is the maximum number of children the mini-buses can still take?
Level 3 PSLE
A shelf can be packed from end to end with 30 large books or 40 small books. Andy already packed the shelf with 5 large books and 25 small books. At most, how many more large books can Kevin pack the shelf with?