If a+b=c and b+c=d and c+d=e and a=7 and e=5, find a+b+c+d+e.

Answer 1

a=7,e=5, so
c+d=5
b+c=d
7+b=c

b = c-7
d = 5-c

b+c=d
c-7 + c = 5-c
3c = 12
c=4
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