Hey there! I'm happy to help!
The unit rate is how much stuff there is per 1 unit. All ratios can be rewritten as fractions, this one could be 0.2/0.5. The word per means divide, and fractions are basically dividing. So, we want the denominator to be 1.
To get 0.5 to 1, we multiply by 2. So, we will multiply the fraction by 2/2.
0.2/0.5(2/2)=0.4/1
Therefore, the unit rate is 0.4/1 or 0.4:1 or 0.4 per 1.
Have a wonderful day! :D
Part 1: I'm pretty sure B is soluble in water.
Part 2: The data is showing that A isn't soluble at all (probably cause it's solid or a lipid or something) because the amount undissolved stays the same as B changes in solubility.
The answer in simplest form is 1/4.
This answer 30 because 75+75=150
180-150=30