Sandy sold half of her comic books and then bought 9 more. she now has 12. how many did she begin with write an equation and solve. me

Sandy began with a number of books that we don't know. Since that number is unknown to us, we use a variable to represent it. Let x = the number of books Sandy began with.

Sandy sold half of her comic books.

She sold x/2 books, and she kept x/2 books.

She kept x/2 books. Then she bought 9 books.

Now she has x/2 + 9 books. We are told she now has 12 books.

That means x/2 + 9 must equal 12. That gives us the equation.

Now we solve the equation. We subtract 9 from both sides.

Multiply both sides by 2.

Since we let x equal the number of books she began with, now we know she began with 6 books.

She began with 6 books.

x = ±sqrt(10)

step-by-step explanation:

5 - 2x² = -15

subtract 5 from each side

5-5 - 2x² = -15-5

-2x^2   = -20

divide by -2 on each side

-2x^2   /-2= -20/-2

x^2 =10

take the square root on each side

sqrt(x^2 )=±sqrt(10)

x = ±sqrt(10)

check:

5 - 2x² = -15

+sqrt(10)

5 - 2(sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15

-sqrt(10)

5 - 2(-sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15

step-by-step explanation:

what is the figure? attach a picture.