HALF OF MAJOR AND MINOR MATH QUESTION!!!!

I have this math problem I can't figure out:
if x = 7, then 3x = 3•7

I need the property of this. I'm guessing it's multiplicative but I'm not sure

Another guess is Multiplicative Property Of Equality

Please help

Thanks

Multiplicative Property Of Equality is correct

It states that

If A=B

Then AC=BC

So since 7=X

then 3X=3*7

Looks like substitution to me.
Or the law that says equals time equals are equal.