What is the distributive property of 10x+12

I assume you’re asking how to use the distributive property to rewrite that expression. 10 and 12 both have 2 as a common factor; we can rewrite 10 as 2 (5) and 12 as 2 (6). Rewriting our whole expression, we have

2 (5x) + 2 (6)

The distributive property states that, for any three numbers a, b, and c:

a (b + c) = ab + ac

And we can play this property back in reverse on our expression to obtain a new one (our answer):

2 (5x) + 2 (6) = 2 (5x + 6)