first 3/4: this is actually 0.75. but the percent means we have to divide it by 100:
0.0075
3/25 is actually 0.12 (because it's equal to 12/100: i multiplied both numbers by 4)
and if it's a percent, again we "move to "move the point" or in other words divide by a 100:
0.0012 (think of dividing by 10 as of moving the coma to the left and adding zeros if there is noone to move)
the last one is equal to 55/100 (multiplied both by 5), so 11/20 % is 0.0055
I hope this was clear, let me know if you have questions!