Sort of. You divide the stake by the number on the right and multiply it by the figure on the left.
9/1 = £10 divided by one times nine = £90 (plus your stake back) = £100
7/2 = £10 divided by two times seven = £35 (plus your stake back) = £45
The number certainly go over 9 and prices of 150/1 are not unusual for nags with no chance.
The more people put a bet on, the lower the odds become. So if a horse started out at 33/1 and a lot of money was bet on it, the odds would shorten to say 12/1 or even lower like 5/1
Most bookmakers allow you to "take a price" meaning that if you back it at 33/1, you get those odds even if the horse comes in at 5/1. The disadvantage is that if the horse goes out to 50/1, you would still only get 33/1. (Although some bookmakers offer "best odds" on some races which would pay out at 50/1 even if you took a lower price)