Question: hi this week i have some tutorial work to do...

Hi, this week I have some tutorial work to do on ratios. I have a few questions here which I am not too sure on how to do them, one of which I have posted below. This topic is always one that is a bit hard for me to understand, so if you could, I'd prefer working out and explanation where necessary. Thank you.

 

Question:

On one campus ofa university there are 3rd year, 2nd year and 1st   year students in the ratio of 3 : 5 : 7. If there are 306, 3rd year students how many students are there altogether and how many 1st   year students are there?