(i forgot what the commutative property of addition was. answer fast. )

which shows the commutative property of addition?

a. 15 + ( 43 + 9 ) = ( 15 + 43 ) + 9

b. 15 + 18 = 30 + 3

c. 15.4 + 23.1 = 23.1 + 15.4

d. 27 + 0 = 27

What is the quadric regression equation that fits these data

The manufacturer of a new product developed the following expression to predict the monthly profit, in thousands of dollars, from sales of the productwhen it is sold at a unit price of x dollars.-0.5x^2 + 22x - 224what is represented by the zero(s) of the expression? a.the profit when the unit price is equal to 0b.the unit price(s) when the profit is equal to 0c.the profit when the unit price is greatestd.the unit price(s) when profit is greatest

Yesterday i ran 5 miles. today, i ran 3.7 miles. did my percent increase, decrease or is it a percent error? plz i need