Sagot :
si x/y =2/5 alors x = 2/5 * y = 2y/5
si y/z = 9/7 alors y = 9/7*z donc z = y/(9/7) = 7y/9
donc x/z = (2y/5)/(7y/9) = (2y/5)*(9/7y) = 18y/35y = 18/35
si y/z = 9/7 alors y = 9/7*z donc z = y/(9/7) = 7y/9
donc x/z = (2y/5)/(7y/9) = (2y/5)*(9/7y) = 18y/35y = 18/35