DEar Helen, It is important to fololow your valve and at the first sing of a decrease in the pumping function of your heart to have this repaired. You may just require a MV repair. The tricuspid regurgitation will often correct once the mitral leak is fixed.
It is most likely that your mitral valve was affected by rheumatic disease and that your tricuspid leaks because the mitral leaks (it is a closed circuit with the tricuspid relieving pressure from the mitral valve.)