Question

difference of two numbers is 9 and their ratio is 7 is to 4 calculate the numbers

Answer 1

Let one number be x
Then difference of two numbers are 9
So other number will be x+9
x+9/x=7/4
4x+36=7x
3x=36
x=12
Other num =x+9=21
So the numbers are 12 and 21

Answer 2

let the no be x and y

the equation will be x–y=9. eqn 1
the other no. will be x/y=7/4
4x=7y
4x–7y=0. eqn 2
multiply eqn 1 by 4 and add eqn 1 and 2

4x– 4y=36
4x– 7y=0

3y=36
y=12

put in eqn 1
x–y=9
x–12=9
x=9+12
x=21

hope this will help you