She spent $75
The best news of this problem is that the books all cost the same.
So 8 + 3 + 4 = 15 books total
15 x $5 = $75
A binomial squared is written like
So, we have 
So, we want to complete the square 
We can add and subtract 9 to write
Answer:
A theorem is a general proposition not self-evident but proved by a chain of reasoning; a truth established by means of accepted truths.
Step-by-step explanation:
It will be c- 20:
4q and 2(q+30) have to equal the same therefore q=30 which makes both these equations equal.
3p + 4q then have to equal 180 as they are on a straight line so you know q=30 so 4x30=120 so 180-120=60
Then 60/3=20 and that is your answer.
Hope this helps :)
Answer:
3.4
Step-by-step explanation:
Standard deviation of a population is defined as:
σ² = ∑(xᵢ − μ)² / n
The standard deviation of a sample is defined as:
s² = ∑(xᵢ − x)² / (n - 1)
It's not clear which one we have, so let's calculate both.
First, we must find the mean.
μ = (5+12+15+10+12+6+8+8) / 8
μ = 9.5
Now we find the squares of the differences:
(5-9.5)² + (12-9.5)² + (15-9.5)² + (10-9.5)² + (12-9.5)² + (6-9.5)² + (8-9.5)² + (8-9.5)²
= 80
Divide by n:
σ² = 80 / 8
σ² = 10
And take the square root:
σ = √10
σ ≈ 3.2
That's not one of the answers, so let's try the standard deviation of a sample instead of a population.
Instead of dividing by n, we'll divide by n-1:
s² = 80 / 7
And take the square root:
s = √(80/7)
s ≈ 3.4
So that must be it.
