Răspuns :
a=108-b
108-b-b=42
108-2b=42
-2b=42-108
-2b=-66/×(-1)
2b=66
b=66:2
b=33
a+33=108
a=108-33
a=75
108-b-b=42
108-2b=42
-2b=42-108
-2b=-66/×(-1)
2b=66
b=66:2
b=33
a+33=108
a=108-33
a=75