So, you put pg/min, so 12/18 = 22/x . And then there is two ways you could go, and i will show you the way i do it.
You cross multiply and so you get 18*22=12*x
And then you multiply 18*22(396) and multiply 12 times x(12x)
so your equation now is 396=12x. And you need to get the "x" alone on one side so you divide both sides by 12.
396 divided by 12 is 33. So it will take her 33 minutes.
It looks like the picture below
