Answer:
D is the correct answer
Step-by-step explanation:
Please mark me as brainlist thanks
Well, for 20 you just add them, to get

. For 21, you do a substraction:

. It'd take him quite some time (does this one even have zeros? :)) )
Step-by-step explanation:
Are
Bsushdid djjdu
Dhhduehehid
Dhdhuduhdje