I have attached a file of attempt :) Dont know how to find x
For which question have you posted this attempt?
Lets take the second for instance where b is inversely proportional to a^2.
We can write ##b \propto \frac{1}{a^2}##. Removing the proportionality sign, ##b =\frac{k}{a^2}## where ##k## is some constant.
Substitute ##a## and ##b##, find the value of k.