I'd like you to correct this sentence.

If you want to make the same osmotic pressure, you need to add sugar 9 times as much as salt to water

If you want to create the same osmotic pressure, you will need to add a 9 to 1 ratio of sugar to salt into water. 

I'm sure there are better ways to word it! I hope I helped though, and good luck!

I'd like you to correct this sentence.

If you want to have the same osmotic pressure, you need to add 9 times the amount of sugar to the water as there is salt.

Or

If you want to have the same osmotic pressure, you need 9 times more sugar than salt in the water.

Or as Victor said:

If you want to have the same osmotic pressure, you need a sugar-to-salt ration of 9:1.

I'd like you to correct this sentence.

If you want to make the same osmotic pressure, you need to add sugar 9 times as much as salt to water

If you want to maintain the same osmotic pressure, you need a 9:1 salt-to-sugar ratio.