The angle does not matter. Think of it as finding the other side to a triangle. Use

a=39 (line AB)
b=b (the leg we need to find)
c=89 (line BD)


(subtract the 1521 from both sides)

(square root both sides)

b = 80
AD=80
Answer:
No
Step-by-step explanation:
There are two values for x=0
Not sure if I quite understand your question. But ill assume that you're asking if 1 times 7 is positive. Or if 1x7 is positive.
1 times 7 equals 7 so it is a positive integer.
1x7 can be positive or negative depending on what x equals. If x is a negative number then the whole expression is negative. If x is postive the expression is positive.
A.
If she will choose 8 from 12 photos, the total number of ways she can choose is given by a combination of 12 choose 8, since the order of the photos doesn't matter.
The formula for a combination of n choose p is:

For n = 12 and p = 8, we have:

So there are 495 ways.
B.
If she wants to arrange the 12 photos, the total number of ways is given by the factorial of 12:

There are 479,001,600 ways.
C.
Since 10 photos already have specific places, we need to calculate the number of ways to arrange the other two photos in the two remaining places.
In this case, there are only 2 ways of organizing the remaining two photos:
Photo 1 first, photo 2 last, or photo 1 last and photo 2 first.