Answer: -5.6
Step-by-step explanation:
Simplifying
(4x + -28) = 9x
Reorder the terms:
(-28 + 4x) = 9x
Remove parenthesis around (-28 + 4x)
-28 + 4x = 9x
Solving
-28 + 4x = 9x
Solving for variable 'x'.
Move all terms containing x to the left, all other terms to the right.
Add '-9x' to each side of the equation.
-28 + 4x + -9x = 9x + -9x
Combine like terms: 4x + -9x = -5x
-28 + -5x = 9x + -9x
Combine like terms: 9x + -9x = 0
-28 + -5x = 0
Add '28' to each side of the equation.
-28 + 28 + -5x = 0 + 28
Combine like terms: -28 + 28 = 0
0 + -5x = 0 + 28
-5x = 0 + 28
Combine like terms: 0 + 28 = 28
-5x = 28
Divide each side by '-5'.
x = -5.6
Simplifying
x = -5.6
Answer:
There is a 99.99998% probability that at least one valve opens.
Step-by-step explanation:
For each valve there are only two possible outcomes. Either it opens on demand, or it does not. This means that we use the binomial probability distribution to solve this problem.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.
In which 
is the number of different combinatios of x objects from a set of n elements, given by the following formula.
And p is the probability of X happening.
In this problem we have that:
Calculate P(at least one valve opens).
This is 
Either no valves open, or at least one does. The sum of the probabilities of these events is decimal 1. So:
So
Finally
There is a 99.99998% probability that at least one valve opens.
Answer:
7 books
Step-by-step explanation:
make an equation
x = # of books each book is $4 so its 4x
the shipping fee no matter how many books he buys will be $2 so it's just 2
the equation looks like this:
4x + 2 = 30
we set equal to 30 cuz he can't spend more than $30
solve for x
4x = 30 -2
4x = 28
x = 7
Brett can buy no more than 7 books.
