Răspuns :
a+100+200=100+300
a+100+200=400
a+100=400-200
a+100=200
a=200-100
a=100
a+100+200=400
a+100=400-200
a+100=200
a=200-100
a=100
A+100+200-300=100
A+100+200=100+300
A+100=400-200
A = 200-100
A= 100