dividing both the numerator and the denominator by 9 you'll have
0.9/9 = 0.1
756/9 = 84
so you'll have it as
0.1/84
remember that you still have a decimal number at the numerator.. in order to have it as a whole number then we multiply both the numerator and denominator with 10 making the expression:
0.1 x 10 = 1
84 x 10 = 840
so you'll have it as 1/840 not 840