Question

if the difference between 75% of a number and 4/5th of that number is 40. what is the number?

Answer 1

let the no. be x
x75/100-4x/5=40
3x/4-4x/5=40
(15x-16x)/20=40
-x/20=40
=>x=-80

Answer 2

Let the number be
$x$
The question says,
either
$0.75 x - \frac{4}{5} x = 40$
or
$\frac{4}{5} x - 0.75 x = 40$
As
$\frac{4}{5} x = 0.8x$
Either
$0.05x = 40$
or
$-0.05x = 40$
x
becomes
$800$ or $-800$