Which statement shows the associative property of addition? 7⋅(4⋅x)=(7⋅4)⋅x

13 + 5a = 5a + 13

(d + 4) + 17 = 17 + (d + 4)

(18 + 6) + y = 18 + (6 + y)

In one day there are too high tides into low tides and equally spaced intervals the high tide is observed to be 6 feet above the average sea level after six hours passed a low tide occurs at 6 feet below the average sea level in this task you will model this occurrence using a trigonometric function by using x as a measurement of time assume the first high tide occurs at x=0. a. what are the independent and dependent variables? b. determine these key features of the function that models the tide: 1.amplitude 2.period 3.frequency 4.midline 5.vertical shift 6.phase shift c. create a trigonometric function that models the ocean tide for a period of 12 hours. d.what is the height of the tide after 93 hours?