Rupert is $$\frac{3}{5}$$ as old as his brother. In 21 years’ time, he will be $$\frac{5}{6}$$ as old as his brother. <hr> How old will Rupert be in 21 years’ time?<br> <input min="0" type="number" id="imp6pg058q14_1" class="lineinput" placeholder="?">