Answer:
There is nothing to multiply.
Step-by-step explanation:
the area of a triangle is
baseline × height / 2
in our case
baseline × 5 / 2 = 20 in²
baseline × 5 = 40
baseline = 8 in
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.
![2x+5\le 15](https://tex.z-dn.net/?f=2x%2B5%5Cle%2015)
Let's solve.
![2x+5\le 15\\ \\ 2x\le 15-5\\ \\ 2x\le 10\\ \\ x\le \frac { 10 }{ 2 } \\ \\ x\le 5](https://tex.z-dn.net/?f=2x%2B5%5Cle%2015%5C%5C%20%5C%5C%202x%5Cle%2015-5%5C%5C%20%5C%5C%202x%5Cle%2010%5C%5C%20%5C%5C%20x%5Cle%20%5Cfrac%20%7B%2010%20%7D%7B%202%20%7D%20%5C%5C%20%5C%5C%20x%5Cle%205)
![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,
That would be a total of 32
-4+x=9.5
x=13.5
The student might have subtracted 9.5-4, which results in the answer 5.5. The correct answer is 13.5.