2x-1=5
2(3)-1=5
6-1=5
5=5
x=3
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
You are correct my dad is a math expert!!
Got this and not sure but best luck with your studying