I went to Half Priced Books and purchased 15 books. I paid $2 each for some and $3 each for the rest of the books. How many $2 books did I buy if I spent $34?

Thus the number of books at $2 is 9 books.

Step-by-step explanation:

The number of the book purchased = 15 books

Total amount spend to buy the books = $34

The prices of books are $2 and $3.

Let the number of books purchased at price  $2 = x

Let the number of books purchased at price  $3 = y

Now we have to find the number of books that is bought at $2.

Below are the equations.

x + y = 15

2x + 3y = 34

Now solve for the x,  

x + y = 15

y = 15 – x

Now insert it in the 2x + 3y = 34

2x + 3(15-x) = 34

2x + 45 – 3x = 34

-x = 34 – 45

x = 9

Thus the number of books at $2 is 9 books.

according to the triangle sum theorem, all the angles in a triangle must add up to 180 degrees. if we know one angle is already 90, we do 180-90=90. the other 2 angles must add up to 90, exactly.

step-by-step explanation:

the polynomial is a perfect square trinomial of the form a^2-2ab+b^2:

option a. true

step-by-step explanation:

9x^2-12x+4

comparing with the form a^2-2ab+b^2

1.) a^2=9x^2

solving for a: square root both sides of the equation:

sqrt(a^2)=sqrt(9x^2)

a=sqrt(9) sqrt(x^2)

a=3x

2.) b^2=4

solving for b: square root both sides of the equation:

sqrt(b^2)=sqrt(4)

b=2

to be a perfet square trinomial 2ab must be equal to 12x. let's check:

2ab = 2 (3x) (2)

2ab = 12x

correct