A 
rational number is any number that can be written as the 
ratio between two other numbers i.e. in the form 

Part A:
An easy choice that makes sense is 7.8, right in the middle. To prove that it's rational we need to write it as a ratio. In this case we have 

Part B:
We need a number that can't be written as a ratio (because it neither terminates nor repeats). Some common ones are 

, 

, 

 and 

 so it makes sense to try and use those to build our number. In this case 

 works nicely. 
 
        
        
        
Answer:
240
Step-by-step explanation:
We know that 50% of the number is 150 so we can assume the number is 300(if its 50% just double that number). Next we use the equation 0.80 x 300 which gives us the answer 240.
Hope I helped
 
        
                    
             
        
        
        
Answer:  
1st Question
A. 85
2nd Question  
B. 71
Step-by-step explanation:
1st Question
{90 + 94 + 96 + 90} = 370/4 = 92.5
{95 + 99}                  = 194/2 = 97
{87 + 75 + 82 + 85} = 329/4 = 82.25
{71}                =  71/1               = 71
.20(92.5) +.25(97) +.30(82.25) +.25(71) = 85.175  Rounded-up = 85
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2nd Question  
.10(95) +.20(80) +.50(67) +.20(60) = 71