MAth Can be tricky. here are some links to help:
Addition:
Column Addition
Partial Sums
Partial Sums (additional video)
Subtraction:
Counting Up Method
Counting Up Method
Counting Up Method on a Number Line
Subtracting 3 Digit Numbers With Zeros
Trade First
Traditional Subtraction Method
Extend and Trade Subtraction
Multiplication:
Partial Products Multiplication
Lattice AND Traditional Multiplication
Bow Tie Method
Fast trick to multiply 2 digit numbers
Division:
Partial Quotients
Column Division