Anyway, here is one of the questions on the practice paper that I'm currently struggling with:

The weights of the 20 students are shown in the following diagram (in kg). The median weight is 67kg.

__Stem (Tens)__

**Leaf (Units)**

__5__

**3 4 6 8 9**

__6__

**1 2 4 6 6 y**

__7__

**2 4 6 7 8**

__8__

**3 x 3 9**

Find x and y.

Thank you in advance! Oh, and if possible, please explain on how to solve the question without giving out the answer as I'd like to attempt it on my own.