teacher please solve and give only two some that is 7th and 12th

Dear Student
Given that monthly pocket money of ravi and sanjeev are 5:7
so let

Monthly pocket money of ravi and sanjeev be=5x and 7x  
And given expenditure are in ratio 3:5 So,
Expenditures=3y and 5y
Given that they save Rs 80
5x-3y=80  (1)7x-5y=80  (2)
Multiplying eqn 1 with 5 and eqn 2 with 3 we get

25x-15y=40021x-15y=240-       +     - 4x=160

x=40 

and y=40 So we get monthly pocket money of Ravi=Rs 200
And pocket money of sanjeev is Rs 280.

Ask remaining queries in seperate thread.
Regards.

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