Any number you substitute for "a" will work. You can substitute fractions, decimals, negative numbers, or whole numbers. What you wrote is correct, but you do not just need to use positive whole numbers.

For example 3 * .25 = .25 + .25 + .25

.75 = .75

The equation balances and your answer is correct.

I would go one more step with the three number sentences that you did and show the final step. For example, in your number sentence 3 * 2 = 2 + 2+ 2, I would finish it off and prove that it balances by writing 6 = 6. This will help you develop better skills as you get to more complex problems.

3*a = a+a+a.

This an identity as the left side of the equation 3*a or 3a or 3times a number. The right side of the equation is a+a+a = 3a. So both sides are the same algebraically and so this an identity.

An identity is true for any value of the variable.

So we can give example of the pattern 3*a = a+a+a for any value of a.

Examples

3*2 = 2+2+2

3*5 = 5+4+5

3*100 = 100+100+100

3* 1003 = 1003+1003+1003 etc.