Strategy 1: Using Manipulatives or objects
Step 1: Take some colored buttons ( 20 buttons) on a check board.
Step 2: Speak aloud that you are taking away 5 buttons from the 20 kept on the check board.
Step 3: Ask children to do back ward counting starting from 20 and reach the number which is left after removing 5 buttons.
You can apply this technique by calling every child in the class or make groups of 2 and give each group buttons or cards made of chart paper to do this activity.
Strategy 2: Count Back
Step 1: You can use a colored chalk for this.
Write a two digit number( ex 12) on the board and ask students to remove the number from it (ex 3)
12 ◊ ◊ ◊
11 10 9
equation will be= 12 -3= 9
put the bigger number in your head and draw dots to help you count back and find the difference
Strategy 3: Visualize when solving word problems
Step 1: Ask students to visualize what is given in the word problem. for eaxmple :
Meera had 8 candies. She gave 3 candies to her friend. How many was she left with?
Step1: Meera= Ο Ο Ο Ο Ο Ο Ο Ο
Step 2: She GAVE= Ο Ο Ο
Step 3: Meera was left with=
Refer to the site for more clarity: https://susanjonesteaching.com/subtraction-activities-first-grade/