Yes. Because the x and the 5 can change in same ways.
Yes they do.
Yea X means another number
Yes. Because the x and the 5 can change in same ways.
the order of the factors does not alter the result
When adding, the order does not matter. It's called the summation property.
5 + 5 = 10. This is the same as 5 x 2.
(x + 4) + (x + 5) = 2x + 9
Yes.
(x + 4) + (x + 5) = 2x + 9
x = 15
5+x=x+5 is an example of the commutative property of addition.