"percent" means "per cent" which means "per 100".
"Percent" means "divided by 100.
As a fraction, just write the percent over 100.
a. 13.5% = 13.5/100 = 135/1000 = 0.135
b. 12.5% = 12.5/100 = 125/1000 = 0.125
c. 3.8% = 3.8/100 = 38/1000 = 0.038
d. 0.5% = 0.5/100 = 5/1000 = 0.005
