Let total number of post card = x

and total number of inland letters = y

Given, total number of post cards and inland letters purchased = 60

=> x + y = 60   ..........1

Again, Post cards costing 15 paise each and inland letters costing 75 paise each were purchased for Rupess 33

=> 15x/100 + 75y/100 = 33          {since 15 paise = 15/100 Rupee}

=> 3x/20 + 3y/4 = 33

=> 3(x/20 + y/4) = 33

=> x/20 + y/4 = 33/3

=> x/20 + y/4 = 11

=> (x + 5y)/20 = 11

=> x + 5y = 11 * 20

=> x + 5y = 220 ......2

Put value of x from equation 1 in equation 2, we get

=> 60 - y + 5y = 220

=> 60 + 4y = 220

=> 4y = 220 - 60

=> 4y = 160

=> y = 160/4

=> y = 40

From equation 1, we get

       x + 40 = 60

=> x = 60 - 40

=> x = 20

So, total number of post card = 20

and total number of inland letters = 40