a) a+b=247
-b=97-c => b=c-97
159+c=312 => c=312-159 => c=153
Inlocuim : b=c-97 => b=153-97 => b=56
Inlocuim : a+b=247 => a+56=247 => a=247-56 => a=191
b)a-b=325
b=177+c
c=135+95=> c=230
Inlocuim : b=177+230 => b= 407
Inlocuim : a+b=247 => a+407=247 => a=247-407 => a=-160