First of all, saying you're terrible at maths will make you terrible at maths. Never say that again!

As for evaluating the quartiles, it's easiest to split your data into two halves and evaluate the median of each of the halves. Each half consists of three terms, and so the quartiles will be the middle term in each half. So the first quartile is 5 300 000 and the third quartile is 6 100 000.