Question

The difference of 2 positive numbers is 81 and quotient obtained on dividing the one by the other is 9. find the first number.

Answer 1

Let x be the first number,
x= first number
And since their difference is 54, you can have 54+x as your second number.
x= 1st Number
54+x= 2nd Number 
If we divide them, we have
54+x/x = 4
By cross-multiplication, we have
54+x = 4x
Then transpose,
54 = 4x-x

Simplify,
54 = 3x
Then divide both side by 3
54 = 3x
18 = x
Therefore, the first number is 18 and the second number is 72. 
CHECKING :)
54+18/18=4
72/18=4
4=4 
GOTCHA XD