TBR Physics, pressure

[redbird1133]

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I'm really struggling with these pressure questions, can anyone please explain?! In book II, example 7.2a:

At a specific depth in a swimming pool, a barometer measures the total pressure to be twice that of atmospheric pressure. if the barometer is now submerged to a depth that is twice its initial depth, by how much does the total pressure increase?
a. increase by 50%
b. increase by 100%
c. increase by 200%
d. increase by 300%

Intuitively I would have put a here, which is correct but when I try to solve it I don't get it.
I was using the equation P1-P2 = rho (y2-y1)g
So i got P1-P2 = rho (2-1) because the barometer is submerged to a depth 2x the initial, I don't get where to go from here and the explanation makes no sense to me, somehow they get 3Patm/2Patm

 

[el_duderino]

Surface is 1 atm.

At depth x, pressure is 2 atm. That's an increase of 1 atm.
At depth 2x, pressure would increase 1 more atm for a total of 3 atm. Going from 2 to 3 atm is an increase of 50%.