TAX CALCULATION PROBLEM

Hello, 

Please could you help me regarding the tax calculation method I need to calculate the tax as shown below: 

1. Get the sub total (X)

2. Calculate 10 % service tax (y) and add to the total (x) , total = x+y = z

3. calculate the 16% sales tax (s) whixh is (z*16%)+z to get the Total

Please any suggestions??