100-(30+30)-(20-10)-15+15)

Răspuns :

100-(30+30)-(20-10)-(15+15)=
100-60-10-30=
40-10-30=
30-30= 0
=100-(30+30)-(20-10)-15+15)
=100-60-10-30=
=40-10-30=
=30-30=
=0