Answer :

divide 18 by 3 and double it to get 12 :))))))

number that we find = A
A x 150/100=18
simplify 150/100=3/2
A x 3/2=18
divide both side by 3/2
A=18/(3/2)
A=18 x 2/3 
A=12
the number that 150% of it is 18 = 12