It can help because 9×4 =36, and 9×8=72. if you divide 72 by 2 you get 36 which is the answer to 9 ×4. basically because nine is the same in both problems you are multiplying by 4 (and you know 4 is half of 8) you can assume that multiplying the sum of 4 and 9 that you will get the sum of 8 and 9.
Answer:
r=1
Step-by-step explanation:
-4 r -10r + -5= -19
-4r + (-10r) + -5=-19
-14r+ -5 = -19
-14r + -5 +5= -19+5
-14r= -14
r=1
The function for the height is

f(0) = 5 cos(0) + 7 = 5 + 7 = 12 (verified)
The period is T = 12 hours.
After 4 hours (t = 4), the height is

A graph of f(t) confirms the answer.
Answer: 4.5 ft
There may be more than one way in which to answer this question. I will assume that the "equation" is a linear one: f(x) = mx + b.
Then (16/3) = m(1) + b
This is one equation in two unknowns, so it does not have a unique solution. Was there more to this problem than you have shared?
If we assume that the y-intercept (b) is zero, then y = mx, and
16/3 = 1m, so that m = 16/3, and so y = (16/3)x.