I start with the unknowns. We dont know Ram's and Raheem's income. Normally, we need two variables for this, but we know that their income's are in the ratio 9:7. So, we can manage with one variable.

Let Ram's income be 9x. You might ask "why 9x and not x?". I use 9x because this makes Raheem's income 7x. It makes the calculations simpler.

The other unknown is their expenses. Let Ram's monthly expenses be 4y. Then, Rahim's monthly expenses would be 3y.

Now, we write down the equations:

Ram's savings are 1600  per month.

Ram's savings = Ram's income - Ram's monthly expenses

Ram's savings = 9x - 4y = 1600

Raheem's savings = 7x - 3y = 1600

This gives us two equations in two variables, x and y.

Eq 1: 9x - 4y = 1600

Eq 2: 7x - 3y = 1600

There are many ways of solving these two equations.

How did you solve this? Did you do this differently?