2.25 is 1.5% of a number

2.25 =x*1.5%

2.25 = x*1.5/100

2.25 *100 =x*1.5

225/1.5    = x

150          =x

Just subtract 1.5 from 100.  Now, multiply 2.25 by that.  I would give you the answer, but that would be cheating.  

2.25=1.5%of x

2.25=0.015X

X=2.25/0.015