To rearrange a formula, it is required that you group variables in certain ways, to leave you with the desired form.
For example,
Rearrange y=3x^2+3 to make x the subject.
Firstly, we want to isolate the x, and try and work out how we can get it to become just x on its own.
To do this, first subtract all the constants from the right hand side of the equation:
y-3 = 3x^2
Now manipulate the left hand side to leave you with x:
x^2 = (y-3)/3
x = ((y-3)/3)^(1/2)