You must make a chart for the sample space of all possible
dice throws:
 
Here is the sample space. It contains 64 possible outcomes:
(1,1)  (1,2)   (1,3)  (1,4)   (1,5)  (1,6)  (1,7)  (1,8)
(2,1)  (2,2)   (2,3)  (2,4)   (2,5)  (2,6)  (2,7)  (2,8)
(3,1)  (3,2)   (3,3)  (3,4)   (3,5)  (3,6)  (3,7)  (3,8)
(4,1)  (4,2)   (4,3)  (4,4)   (4,5)  (4,6)  (4,7)  (4,8)
(5,1)  (5,2)   (5,3)  (5,4)   (5,5)  (5,6)  (5,7)  (5,8)
(6,1)  (6,2)   (6,3)  (6,4)   (6,5)  (6,6)  (6,7)  (6,8)
(7,1)  (7,2)   (7,3)  (7,4)   (7,5)  (7,6)  (7,7)  (7,8)
(8,1)  (8,2)   (8,3)  (8,4)   (8,5)  (8,6)  (8,7)  (8,8)
You'll find that all throws with a given sum are on a diagonal.
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a:P(4)
The throws with sum 4 are in red:
(1,1)  (1,2)   (1,3)  (1,4)   (1,5)  (1,6)  (1,7)  (1,8)
(2,1)  (2,2)   (2,3)  (2,4)   (2,5)  (2,6)  (2,7)  (2,8)
(3,1)  (3,2)   (3,3)  (3,4)   (3,5)  (3,6)  (3,7)  (3,8)
(4,1)  (4,2)   (4,3)  (4,4)   (4,5)  (4,6)  (4,7)  (4,8)
(5,1)  (5,2)   (5,3)  (5,4)   (5,5)  (5,6)  (5,7)  (5,8)
(6,1)  (6,2)   (6,3)  (6,4)   (6,5)  (6,6)  (6,7)  (6,8)
(7,1)  (7,2)   (7,3)  (7,4)   (7,5)  (7,6)  (7,7)  (7,8)
(8,1)  (8,2)   (8,3)  (8,4)   (8,5)  (8,6)  (8,7)  (8,8)
Therefore P(4) is 3 out of 64 or 
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b:P(6)
The throws with sum 6 are in red:
(1,1)  (1,2)   (1,3)  (1,4)   (1,5)  (1,6)  (1,7)  (1,8)
(2,1)  (2,2)   (2,3)  (2,4)   (2,5)  (2,6)  (2,7)  (2,8)
(3,1)  (3,2)   (3,3)  (3,4)   (3,5)  (3,6)  (3,7)  (3,8)
(4,1)  (4,2)   (4,3)  (4,4)   (4,5)  (4,6)  (4,7)  (4,8)
(5,1)  (5,2)   (5,3)  (5,4)   (5,5)  (5,6)  (5,7)  (5,8)
(6,1)  (6,2)   (6,3)  (6,4)   (6,5)  (6,6)  (6,7)  (6,8)
(7,1)  (7,2)   (7,3)  (7,4)   (7,5)  (7,6)  (7,7)  (7,8)
(8,1)  (8,2)   (8,3)  (8,4)   (8,5)  (8,6)  (8,7)  (8,8)
Therefore P(6) is 5 out of 64 or 
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The throws with sum 10 are in red:
(1,1)  (1,2)   (1,3)  (1,4)   (1,5)  (1,6)  (1,7)  (1,8)
(2,1)  (2,2)   (2,3)  (2,4)   (2,5)  (2,6)  (2,7)  (2,8)
(3,1)  (3,2)   (3,3)  (3,4)   (3,5)  (3,6)  (3,7)  (3,8)
(4,1)  (4,2)   (4,3)  (4,4)   (4,5)  (4,6)  (4,7)  (4,8)
(5,1)  (5,2)   (5,3)  (5,4)   (5,5)  (5,6)  (5,7)  (5,8)
(6,1)  (6,2)   (6,3)  (6,4)   (6,5)  (6,6)  (6,7)  (6,8)
(7,1)  (7,2)   (7,3)  (7,4)   (7,5)  (7,6)  (7,7)  (7,8)
(8,1)  (8,2)   (8,3)  (8,4)   (8,5)  (8,6)  (8,7)  (8,8)
Therefore P(10) is 7 out of 64 or 
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The throws with sum 11 are in red:
(1,1)  (1,2)   (1,3)  (1,4)   (1,5)  (1,6)  (1,7)  (1,8)
(2,1)  (2,2)   (2,3)  (2,4)   (2,5)  (2,6)  (2,7)  (2,8)
(3,1)  (3,2)   (3,3)  (3,4)   (3,5)  (3,6)  (3,7)  (3,8)
(4,1)  (4,2)   (4,3)  (4,4)   (4,5)  (4,6)  (4,7)  (4,8)
(5,1)  (5,2)   (5,3)  (5,4)   (5,5)  (5,6)  (5,7)  (5,8)
(6,1)  (6,2)   (6,3)  (6,4)   (6,5)  (6,6)  (6,7)  (6,8)
(7,1)  (7,2)   (7,3)  (7,4)   (7,5)  (7,6)  (7,7)  (7,8)
(8,1)  (8,2)   (8,3)  (8,4)   (8,5)  (8,6)  (8,7)  (8,8)
Therefore P(11) is 6 out of 64 or 
 which reduces to 
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The throws with sum 14 are in red:
(1,1)  (1,2)   (1,3)  (1,4)   (1,5)  (1,6)  (1,7)  (1,8)
(2,1)  (2,2)   (2,3)  (2,4)   (2,5)  (2,6)  (2,7)  (2,8)
(3,1)  (3,2)   (3,3)  (3,4)   (3,5)  (3,6)  (3,7)  (3,8)
(4,1)  (4,2)   (4,3)  (4,4)   (4,5)  (4,6)  (4,7)  (4,8)
(5,1)  (5,2)   (5,3)  (5,4)   (5,5)  (5,6)  (5,7)  (5,8)
(6,1)  (6,2)   (6,3)  (6,4)   (6,5)  (6,6)  (6,7)  (6,8)
(7,1)  (7,2)   (7,3)  (7,4)   (7,5)  (7,6)  (7,7)  (7,8)
(8,1)  (8,2)   (8,3)  (8,4)   (8,5)  (8,6)  (8,7)  (8,8)
Therefore P(14) is 3 out of 64 or 
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The throw with sum 16 is in red:
(1,1)  (1,2)   (1,3)  (1,4)   (1,5)  (1,6)  (1,7)  (1,8)
(2,1)  (2,2)   (2,3)  (2,4)   (2,5)  (2,6)  (2,7)  (2,8)
(3,1)  (3,2)   (3,3)  (3,4)   (3,5)  (3,6)  (3,7)  (3,8)
(4,1)  (4,2)   (4,3)  (4,4)   (4,5)  (4,6)  (4,7)  (4,8)
(5,1)  (5,2)   (5,3)  (5,4)   (5,5)  (5,6)  (5,7)  (5,8)
(6,1)  (6,2)   (6,3)  (6,4)   (6,5)  (6,6)  (6,7)  (6,8)
(7,1)  (7,2)   (7,3)  (7,4)   (7,5)  (7,6)  (7,7)  (7,8)
(8,1)  (8,2)   (8,3)  (8,4)   (8,5)  (8,6)  (8,7)  (8,8)
Therefore P(16) is 1 out of 64 or 
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Edwin