Bonsoir,
1)
a) 100x = 772,72727272....
100 × 7,727272727272.... - 7,7272727272.... = 765
b) 100x - x = 765 ⇒ 99x = 765
⇒ x = 765/99 = (9×85)/(9×11) = 85/11
2) 100 × 8,6363636363..... - 8,6363636363..... = 855
donc : 100x - x = 855
donc : 99x = 855
donc : x = 855/99 = (95×9)/(11×9) = 95/11
