Multiply denominator by whole number then add that number to the nominator. Which would be 5 times 1 plus 3. SO 5+3 IS 8 and you keep the denominator so the first one is 8/5
        
             
        
        
        
Answer:
15 and 20
Step-by-step explanation:
 
        
             
        
        
        
Using the picture, we know (2x+6)+(5x-3)=24. Simplify to find x. 
7x+3=24
7x=21
x=3
We know AB=2x+6, and x=3. Plug 3 in for x.
AB=2(3)+6. 
AB=6+6
AB=12
        
             
        
        
        
<h3>
Answer:  127</h3>
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Explanation:
The phrasing "2/3 of 4/5 of his 2nd exam on his 3rd test" is a bit clunky in my opinion. It seems more complicated than it has to be.
The student got 80 on the second exam. 4/5 of this is (4/5)*80 = 0.8*80 = 64. Then we take 2/3 of this to get (2/3)*64 = 42.667 approximately. If we assume only whole number scores are given, then this would round to 43.
Let x be the score on the fourth exam. Since 5 points of extra credit are given, the student actually got x+5 points on this exam. 
So we have these scores 
- first exam = 70
- second exam = 80
- third exam = 43
- fourth exam = x+5
Adding up these scores and dividing by 4 will get us the average
(sum of scores)/(number of scores) = average
(70+80+43+x+5)/4 = 80
(x+198)/4 = 80
x+198 = 4*80
x+198 = 320
x = 320 - 198
x = 122
So the student got a score of x+5 = 122+5 = 127 on the fourth exam.