HELP Your school is raising money for a non-profit organization. The local chapter of the non-profit organization keeps 80% of the money raised, and 20% goes to the national chapter of the non-profit organization. Four of your friends each donate the same amount. The total money you raise for the local chapter of the non-profit organization is is $51.20. How much does each friend donate?

$16

Step-by-step explanation:

Let x = friends' donations

y = local chapter funds

4x = y

.8y = 51.2

Divide both sides by 0.8 for the second equation

.8y/.8 = 51.2/.8 = 64

Plug in the new y in the first equation

4x = 64

Divide both side by 4

4x/4 = 64/4

x = 16

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