Mark's brother is 5 years older than mark. their combined ages add up to 23. how old is mark?

Mark would be 9

Mark is 9.                                                                      

9+5 =14

14+9=23

correct choice is b

step-by-step explanation:

when you calculate the average rate of change of a function, you are finding the slope of the secant line between the two points. for the function the average rate of change from point to point can be calculated as

to find the average rate of change from day 2 to day 10, note that at day 2, 8 houses were sold, so a(2,8) and at day 10, 2 houses were sold, so b(10,2). thus,