Answer:
- 8 3/4
 - 2, 3
 - 4 1/2, 11 1/4
 - 9 3/4, 16 1/4
 - Y/B = 2/3
 
Explanation:
a)
The first line is simply the sum of the two given numbers.
 3 1/2 +5 1/4 = (3+5) +(2/4+1/4) = 8 3/4
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To find values on the remaining lines, it is convenient to find the ratios of the numbers involved. The ratio of yellow to blue is ...
 Y/B = (3 1/2)/(5 1/4) = (7/2)/(21/4) = (7/2)(4/21) = 2/3
Then ...
 Y : B : total = 2 : 3 : 5
This tells you the numbers on the second line are ...
  Y = 2; B = 3
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The value for B on the third line is the basic ratio number multiplied by (6 3/4)/3 = 2 1/4. Then the other two numbers are ...
 Y = 2(2 1/4) = 4 1/2
 total = 5(2 1/4) = 11 1/4
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The value for Y on the fourth line is the basic ratio number multiplied by (6 1/2)/2 = 3 1/4. Then the other two numbers are ...
 B = 3(3 1/4) = 9 3/4
 total = 5(3 1/4) = 16 1/4
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b)
The equation is the one we used to find the values on the second line:
 Y/B = 2/3