A chemical company makes two brands of antifreeze. The first brand is 85% pure antifreeze, and the second brand is 90% pure antifreeze. In order to obtain 50 gallons of a mixture that contains 50% pure antifreeze, how many gallons of EACH brand of antifreeze must be used?

Let +a+ = gallons of 55% antifreeze needed

Let +b+ = gallons of 95% antifreeze needed

(1) +a+%2B+b+=+160+

(2) +%28+.55a+%2B+.95b+%29+%2F+160+=+.85+

(2) +.55a+%2B+.95b+=+.85%2A160+

(2) +.55a+%2B+.95b+=+136+

(2) +55a+%2B+95b+=+13600+

(2) +11a+%2B+19b+=+2720+

Multiply both sides of (1) by +11+

and subtract (1) from (2)

(2) +11a+%2B+19b+=+2720+

(1) +-11a+-+11b+=+-1760+

+8b+=+960+

+b+=+120+

and

(1) +a+%2B+120+=+160+

(1) +a+=+40+

40 gallons of 55% antifreeze are needed

120 gallons of 95% antifreeze are needed

check:

(2) +%28+.55a+%2B+.95b+%29+%2F+160+=+.85+

(2) +%28+.55%2A40+%2B+.95%2A120+%29+%2F+160+=+.85+

(2) +%28+22+%2B+114+%29+%2F+160+=+.85+

(2) +136+=+.85%2A160+

(2) +136+=+136+

OK

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

i would love   to but there is no graph shown

step-by-step explanation:

i am so sorry