Answer :

There's an infinite number of equivalent ratios for 27:15, these are the ones that just came to my mind:

27:15 = 54:30 (because 27 * 2 = 54 and 15 * 2 = 30)
27:15 = 9:5 (because 27 / 3 = 9 and 15 / 3 = 5)
27:15 = 135:75 (because 27 * 5 = 135 and 15 * 5 = 75)
To get equivalent ratio for the above expression you multiply or divide both the numerator and the denominator by the same number. So, infinite number of ratio is  equivalent to the above expression.

1>  (27/3) : (15/3) = 9 : 5
2>  (27 *2) : (15*2) = 54 : 30
3>  (27*10) : (15*10) = 270 : 150