Răspuns :
123-(30+x)=60
30+x=123-60
x=123-60-30
x=63-30
x=33
Verificare:
123-(30+33)=60
123-63=60
60=60
Solutie:
x=33
30+x=123-60
x=123-60-30
x=63-30
x=33
Verificare:
123-(30+33)=60
123-63=60
60=60
Solutie:
x=33