What rule tells you the 2 and the (9+3) are inseparable?
The distributive property of multiplication tells me that 2(9+3) = 2(9)+2(3) = 18+6 = 24. It is a single expression. It could be 2(a+b) or 2(x+y). The entire expression must be dealt with before the expression is used in the remainder of the equation.
“What rule tells you the 2 and the (9+3) are inseparable?”
2(9+3) = (2*9) + (2*3)
basic algebra