Bruce and Robbie each open up new bank accounts at time $0.$ Brucedeposits $100$ into his bank account, and Robbie deposits $50$ into his. Each account earns the same annual effective interest rate. The amount of interest earned in Bruces account during the $11$th year is equal to X $.$ The amount of interest earned in Robbies account during the $17$th year is also equal to X $.$ Calculate X $.$