1. Problem (17): Calculate $$75 + 3465 + 18162 + 12$$. Add the numbers step-by-step: $$75 + 3465 = 3540$$ $$3540 + 18162 = 21702$$ $$21702 + 12 = 21714$$ Answer: $$21714$$. 2. Problem (18): Calculate $$4672 + 387 + 36 + 9$$. Add step-by-step: $$4672 + 387 = 5059$$ $$5059 + 36 = 5095$$ $$5095 + 9 = 5104$$ Answer: $$5104$$. 3. Problem (19): Calculate $$18564 + 12972 + 864 + 2465$$. Stepwise addition: $$18564 + 12972 = 31536$$ $$31536 + 864 = 32400$$ $$32400 + 2465 = 34865$$ Answer: $$34865$$. 4. Problem (20): Calculate $$5 + 3165 + 72$$. Stepwise: $$5 + 3165 = 3170$$ $$3170 + 72 = 3242$$ Answer: $$3242$$. 5. Problem (21): Calculate $$520 + 5865 + 386 + 9$$. Stepwise: $$520 + 5865 = 6385$$ $$6385 + 386 = 6771$$ $$6771 + 9 = 6780$$ Answer: $$6780$$.