Which expression would represent the cost of one cd, if the total cost for three of them is $36?
1. 3(36)
2. 3 + 36
3.36 - 3

 First option is correct.

Step-by-step explanation:

Since we have given that

Number of CDs = 3

Cost of each CD = $36

We need to find the total cost:

As we need to find the total cost so, we generally use

Number of CDs × Cost of each CD

So, the total cost for 3 CDs is given by

Hence, First option is correct.

b

step-by-step explanation:

ez

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional