The hardcover version of a book sells for 15 dollars and the paperback sells for 11.50. If a store sells 70 copies of the book in one month and charges 917 dollars how many hardcover versions were sold

32 copies of hardcover version.

Step-by-step explanation: Suppose the quantity of hardcover version copies sold is H and the paperback copies is P.

1) A store sells a total of 70 copies:

H + P = 70

2) One hardcover is sold for $15 and one paperback for $11.50. In one month was charged $917:

15H + 11.5P = 917

Solving the system of equations:

H + P = 70 (I)

15H + 11.5P = 917 (II)

Since it is asked for the hardcover version, find H.

Multiply equation (I) by -11.5:

-11.5H - 11.5P = - 805 (III)

Add (II) and (III):

-11.5H - 11.5P = - 805

  15H + 11.5P = 917

  3.5H            = 112

H = 32

In one month, it was sold 32 hardcover version of a book.

the answer is ! ?

hello from mrbilldoesmath!

answer:   (7x + 6y) ( 49x^2 - 42xy + 36y^2)

discussion:

in general, the factorization of a^3 + b^3 is

a^3 + b^ 3 = (a + b) ( a^2 - ab + b^2)

in our case note that 343 = 7^3 and 216 = 6^3 so the equation becomes:

343x^3 + 216y^3 = (7x)^3 + (6y)^3

if you think of a (above) as 7x and b as 6y the factorization becomes

343x^3 + 216y^3 =

((7x + 6y) (   (7x)^2 - 7x*6y + (6y)^2)   =

(7x + 6y) ( 49x^2 - 42xy + 36y^2)

you,

mrb

(a + b) (a^2 - a b + b^2)