Well lets begin by noting that 30% are Grade Eight. That means that 70% will be Grade Six and Seven, but thats not the question, the question is how many people are sixth and seventh grade. As I said before the answer is 84. To find 10% of 120, you shift the decimal point one place to the left and get 12. I earlier said 70% are grade six and seven meaning 70/10=7
All thats left is a simple multiplication problem, 12x7 which gives you 84. To ensure you are correct. 84/7=12 and that promises you a correct answer.
If you do not understand the math I did here reply and I will further explain. For now I hope this helps!
