Ram and Mohan are friends. Each has some money. If Ram gives ? 30 to Mohan, Then Mohan will have twice the money left with Ram. But if Mohan gives ? 10 to Ram, Then Ram will have thrice as much as is left with Mohan. How much money does each have?

Let us assume Ram has R rupees and Mohan has M rupees.
According to question,
If Ram gives 30 rupees to Mohan, then
Ram has left money = R - 30 and Mohan has money = M + 30
Then Mohan will have twice the money left with Ram,
M + 30 = 2(R - 30)
M + 30 = 2R - 60
2R - M = 90................................(1)
Again According to question,
if Mohan gives 10 rupees to Ram, then
Mohan has left the money = M - 10 and Ram has the money = R + 10
Then According to question,
Ram will have thrice as much as is left with Mohan,
R + 10 = 3 (M - 10 )
? R + 10 = 3M - 30
? 3M - R = 10 + 30
? 3M - R = 40..................................(2)
After Multiplying 2 with Equation (2) , add with the equation (1),
6M - 2R + 2R - M = 80 + 90
? 6M - M = 170
? 5M = 170
? M = 170/5
? M = 34
Put the value of M in equation (1), we will get
? 2R - 34 = 90
? 2R = 90 + 34
? 2R = 124
? R = 124/2
? R = 62