Cheri uses her Tune-It-Up music card to make a $12 purchase of a few of her favorite songs. Which integer represents the effect of Cheri's purchase on the balance of her music card? A)−$12
B)−$11
C)$0
D)$12

Step-by-step explanation:

A, -12

if she had an x amount on her card,

after the buys the songs, she will have x-12 left

step-by-step explanation: a reaction is first order. if the initial reactant concentration is 0.0200 m, and 25.0 days later the concentration is 6.25 x 10-4 m, then its half-life is:

the direct variation says that:

then the equation is of the form is given by:

            where k is the constant variation.

from the given table:

consider any value of x and m(x)=y

x = 2 and m(x)=y = 3

substitute these value in [1]; we have;

divide both sides by 2 we get;

⇒

check:

put x = -1 and m(x) = -1.5

substitute in the equation:

-1.5 = -1.5                   true

therefore, the function m(x) represents a direct variation

graph of this function as shown below: