Answer:
Distributive Property
Step-by-step explanation:
The distributive property of multiplication over addition can be used when you multiply a number by a sum.
Let's call that number x, twice the number will be 2x, sum of it and 5 is, 2x+5. So if this expression is at most 15, it means, it can be only less than 15 and equal to 15. Let's show this as an inequality.

Let's solve.

![x\quad \in \quad \left[ -\infty ,5 \right]](https://tex.z-dn.net/?f=x%5Cquad%20%5Cin%20%5Cquad%20%5Cleft%5B%20-%5Cinfty%20%2C5%20%5Cright%5D%20)
If the number is a natural number. The values it can take is,
Answer:
Part A: 38
Part B: 5 or 4 got two different answers
Part C: range because it tells how many numbers are involved apart from the smallest and largest
Step-by-step explanation:
Part A: highest number - lowest number
78-40
Part B
3b because b^2-4= 1/b. So 2/1/b= 2b b+2b = 3b