13.5/3 = 4.5
He hiked for 4.5 hours.
The number of permutations of the 4 different digits is:

The answer is 24 ways.
Answer:
3x - (15 x 3) = 90
or
3x - 45 = 90
Explanation:
there are 3 boxes. We don't know how many are in them yet, so we write this as 3x. However, we know that we give away 15 to 3 different teachers. 15 x 3 = 45
Therefore the first part is 3x - 45
We also know that in the end we have 90 left.
So our final equation is:
3x - 45 = 90
A function can only have one y value for every x value.
the answer is D