a +b=320
b+c=140
a+2×b+c=?


Răspuns :

A + B = 320 B + C = 140 ------------------- A + 2×B + C =? ------------------- A + B = 320        B + C = 140 A + 2×B + C = 320 + 140 A + 2×B + C = 460