(63一21)÷7=42÷7=6
7÷(63—21)=7÷42=1 — 6
(63-21)÷7 =42÷7 =6
(63-21)÷7=42÷7=6
(63÷7)一(21÷7)=9一3=6
亲们,除和除以不一样