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 a+b=7 iar b+c=10 aflati a+3b+2c

Răspuns :

a+b=7
b+c=10
a+3b+2c=?
7+(10+10)=
7+20=27
a + b = 7 
b + c = 10
a + 3b + 2 c =
 7 - b + 3b + 2 ( 10 - b )=
7 - b + 2b + 20 - 2b =
- b = - 20 -7 /-
b = 20 + 7
b = 27