Answer:
I believe the answer is 20
Step-by-step explanation:
Why now :cccccccccccccccccc
The square of a binomial expands as follows:

Expanding all the binomials, we have

Sum like terms:

Simplify terms appearing on both sides:

Move all terms involving k to the left and all numbers to the right:

Divide both sides by -20:

<span>There are 100 * 99 = 9900 different ways to choose two students out of 100 bandmembers. You and our brother are 2 of that ways: you being selected first and you being selected second. Therefore the probability that you two are selected is 2 / 9900 = 0,000202. You can also think as the probability of you being selected among 100 bandmembers, which is 1/100, times the probability of your brother being selected among 99 members, which is 1/99 => (1/100) * (1/99) = 1/ (100*99) = 1 / 9900; plus the same for your brother being selected first and you second => [1/9900] * 2 = 2/9900, which is the same calculated above.</span>
Answer:
The original price of the book was $12.50
Step-by-step explanation:
3x - 0.2(3x) + 10 = 40
30x - 2(3x) + 100 = 400
30x - 6x + 100 = 400
24x + 100 = 400
24x = 300
x = 12.50