based on substitution method

 Let the cost of a bat and a ball be x and y respectively.
According to the given information, we have:

7x+6y=3800

3x+5y=1750

From the first equation,

y = 3800-7x/6

Substituting this value of y in the second equation and simplifying, we get, -17x = -8500

So, x = 500

Thus, we get y = 50

Hence, the cost of a bat is Rs 500 and that of a ball is Rs 50.