HELP I NEED HELP ASAP
HELP I NEED HELP ASAP
HELP I NEED HELP ASAP

10 videos were sold  

Step-by-step explanation:

Hello There!

First we want to create two equations (system of equations)

let c = CD's sold and v = videos sold

a total of 40 CD's and videos we're sold so

40 = c + v

they we're sold for a total amount of $180 ( $4s per CD and $6 per video) so

4c + 6v = 180

now we are going to solve for number of videos sold sold using eliminations and multipliers

first we want to find a common multiple between 4c and c which would be 4

so we multiply 4c + 6v = 180 by -1 and 40 = c + v by 4

(note we have to choose one of the equations to be multiplied by a negative number because we are trying to eliminate some variables)

-1(4c+6v=180) = -4c - 6v = - 180

4(c + v = 40) 4c + 4v = 160

now we combine the equations

4c -4c cancels out

-6v + 4v = -2v

-180 + 160 = -20

we're left with -2v = -20

then we divide each side by -2

-2v/-2=v

-20/-2=10

so the number of videos sold was 10

now to find the number of CDs sold we plug in 10 into v to one of the equations

40 = c + 10

subtract 10 from each side

40 - 10 = 30

we're left with c = 30

so we can conclude that

30 CDs were sold and 10 videos were sold