Answer:
500
Explanation:
Lets make the unknown number the letter a
0.9% can also be shown as 0.9/100
so 0.9 of a = 4.5
x(0.9/100) = 4.5
multiply 0.9 by x
(0.9×a)/100 = 4.5
multiply both sides by 100
0.9×a = 450
divide both sides by 0.9
a = 500
there you have it