Bruce and Robbie each open up new bank accounts at time $0.$ Bruce deposits $100$ 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 Bruce$$s account during the $11$th year is equal to X$.$ The amount of

interest earned in Robbie$$s account during the $17$th year is also equal to X$.$

Calculate X