Addition Rules:

Order Rule: The order of the numbers in a problem does not affect the answer. Example: (6+3=9 is the same as 3+6=9)

Zero Rule: Any number plus zero is the number. Example: (3+0=3; 0+7+7)

One Rule: Any number plus one 1 is one more than the number. Example: (3+1=4; 18+1=19)

Nine Rule: Any single digit number (1-9) added to nine equals the first number minus 1 plus 10. Example: (9+7=6+10=16)

Tens Rule: Any single digit number added to 10 results in the 0 being changed to the number being added to it.

Example: (6+10=16)

Subtraction Rules:

Zero Rule: Any number minus zero equals the number. Example: (7-0=7; 3-0=3; 5-0+5)

One Rule: Any number minus one is one less. Example: (6-1=5; 8-1=7; 3-1=2)

Same Number Rule: Any number minus the same number equals zero. Example: (21-21=0; 1-1=0; 77-77=0)

Ones Less Rule: Any number minus one is the next smaller number. Example: (15-1=14; 8-1=7; 20-1= 19)

BBC Rule: In subtraction when the bottom number is bigger than the top number, break down the top number in the next column, trade it for 10 units, then subtract . Example: (42-7=35 is the same as 30+12-7=35)

Addition/Subtraction Rule: In a subtraction problem, the answer added to the number that is being subtracted equals the top number. Example: (13-5=8, so 8+5=13)