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If a+b=8, a+c=13, b+d=8 and c-d=6 Then what would be the value of a, b, c, d?

0 votes
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If

a+b=8,
a+c=13,
b+d=8,
c-d=6

Then

a, b, c, d  = ??
posted Sep 10, 2016 by anonymous

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3 Answers

+1 vote

Comparing (1) and (2), we notice that
a = d

And comparing (1) and (3), we also notice that
c = b + 5

Armed with this new info, let's play with (4). Substitute a with d and c with b + 5. We'd have:
b + 5 - a = 6

Subtract 5 from both sides to eliminate 5 from the left hand side. It becomes:
b - a = 1
-a + b = 1 .................. (5)
Recall
a + b = 8 .................. (1)
Now we see that (5) has the same variables as (1) so eliminate one variable. If you add both equations, you'd eliminate a, but if you subtract, b goes. Let's add.
-a + a + b + b = 1 + 8
0 + 2b = 9
b = 4.5

but a + b = 8
Therefore
a = 8 - b = 8 - 4.5 = 3.5

d = a = 3.5
Then
c - d = 6
c - 3.5 = 6
c = 6 + 3.5 = 9.5

answer Jan 15, 2017 by Shainkey Jain
0 votes

a=7/2 , b=9/2 ,c=19/2 ,d= 7/2 ...

answer Sep 11, 2016 by Sapna Singh
Please share the working also
–1 vote

answer
a=3.5,b=4.5,c=9.5,d=3.5

answer Sep 17, 2016 by Gangadharan Kv
...