Base on the visibility formula v = 1.225√a, the altitude at which Dereck is hang gliding is 7.4 miles
<h3>How to find altitude using visibility formula?</h3>
The visibility formula is given as follows:
v = 1.225√a
where
- a = altitude
- v = visibility
Therefore,
v = 67.1 miles
v = 1.225√a
67.1 = 1.225√a
divide both sides by 1.225
√a = 67.1 / 1.225
√a = 54.7755102041
square both sides
√a² = √54.7755102041
a = 7.40104789878
a = 7.4 miles
learn more on visibility here: brainly.com/question/16166215
Answer:

Step-by-step explanation:
<u>What number</u> <u>divided by</u> <u>-7</u> <u>is equal to</u> <u>-15</u>
∨ ∨ ∨ ∨ ∨
x ÷ -7 = -15
Multiply -7 to both sides:


I think the answer to this question is 18