a) a= 781-147-293=341
a=540-108+175=607
-a=399-628 <=>a=229
a=279+390=669
-a=99+453-874=-322 => a=322
b)3x+468=639 <=>3x=639-468 <=>x=171/3=57
9a=649-379 <=>9a=270 =>a=30
[tex] \frac{x+396}{4}=185 [/tex] aducem la numitor comun si scapam de fractie si avem : x+396=740 =>x=344
2731a=1731 => a=1
100a=9735-2345 <=>100a=7390 => a=73,9
