#p is defined as 2p-20 for any number p.

#p = 2p-20 --->#(#p) = 2(2p-20)-20 = 4p-60 and thus #(4p-60) = 2(4p-60)-20 = 8p-140 = 12 ---> 8p= 152 ---> p = 19, B is the correct answer.