Answer:
19.741
Explanation:
When subtracting decimals line up the decimals and then add 0s to the end to make it work. SO instead of
21.25
-1.509
___________
It would be
21.250
- 1.509
______________
Solve the subtraction problem like you normally would. THen drop the decimal down so it lies up with the others.
21.250
- 1.509
______________
19.741