Question

when a number is decreased by 40% of itself the result is 270 ..what is the number

Answer 1

it's a kind of an equation
a decreasing by 40% of a number means that 40% is subtracted from it
let's consider x that number
then
x-x*40%=270 i.e. x-x*40/100=270
all you have to do is to solve this equation

Answer 2

if you are attempting to find what number 270 is 40% of, just divide 270 by .4