Answer:
- 273 mL of 5%
- 117 mL of 15%
Step-by-step explanation:
Let q represent the quantity of 15% dressing used. Then the amount of 5% dressing is (390 -q). The amount of vinegar in the mix is ...
   0.15q + 0.05(390 -q) = 0.08(390)
   0.10q = 31.2 -19.5 = 11.7 . . . . . . subtract 0.05(390) and simplify
   q = 117 . . . . . . . . . . . . . . . . . . multiply by 10
   390-q = 273
The chef should use 273 mL of the first brand (5% vinegar) and 117 mL of the second brand (15% vinegar).
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<em>Additional comment</em>
You may have noticed that the value of q is (0.08 -0.05)/(0.10 -0.05)×390. The fraction of the mix that is the highest contributor is the ratio of the difference between the mix value and least contributor, divided by the difference between the contributors: (8-5)/(15-5) = 3/10, the fraction that is 15% vinegar. This is the generic solution to mixture problems.
 
        
             
        
        
        
100 vitamins/2 a day=50 days 50 days/30 days in a month (assumedly)= 5/3 months 1.66
        
             
        
        
        
Answer:
$825.60
Step-by-step explanation:
Since the price of it is $960.00, it means that it's 100%.
100% = 960
1% = 960 ÷ 100 = 9.6
14% = 9.6 x 14 = 134.40
Since they asked for after the discount, deduct the price of the discount with the original price. 
Mountain bike after 14% discount =
960 - 134.40 = 825.60