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2014-10-28T18:39:11+02:00
A-2b=17 ⇒ a=17+2b 
a+b+3c=53⇒17+2b+3c=53⇒3c=53-17-2b⇒c=(36-2b)/3
a+2c=17+2b+[2*(36-2b)/3]=17+2b+(72-4b)/3=(51+6b+72-4b)/3=(123+2b)/3
2 4 2