If 21 out of 24 students did their homework, 3 out of 24 did not do it.
This written as a fraction is 3/24 and can be reduced to 1/8.
This in decimal form is 0.125 .
To convert the decimal to a percent, multiply by 100 and put a percent sign at the end of the number.
0.125 × 100 = 12.5
12.5%