4. A store had 86 DVDs and 52 CDs. When the equal number of DVDs and CDs were sold, the number of DVDs left was 3 times that of the remaining CDs. How many DVDs were
left in the store?​

51 DVDs

Step-by-step explanation:

Let the number of DVDs and CDs sold be x each.

Initial

Number of DVDs= 86

Number of CDs= 52

After selling

Number of DVDs= 86 -x

Number of CDs= 52 -x

Given that there are 3 times as many DVDs than CDs left,

86 -x= 3(52 -x)

Expand:

86 -x= 156 -3x

Bring x terms to 1 side, constant to the other:

3x -x= 156 -86

Simplify:

2x= 70

Divide both sides by 2:

x= 35

Amount of DVDs left

= 86 -x

= 86 -35

= 51

robert puts 2 in each row