Write the following as an expression: How much water do I need to add to l liters of pure alcohol to obtain a solution of 45% alcohol? The answer is an EXPRESSION, not an actual answer

see below

Step-by-step explanation:

amount of water w

l liter of pure alcohol = 100% alcohol

solution is 45 % percent alcohol

total amount of fluid is w+l

(w+l)( .45) = l*.100

Distribute

.45w  + .45 l = 1l

.45 w = 1l - .45l

.45 w = .55l

w = .55l / .45

w =11/9 l

step-by-step explanation:

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