Răspuns :
A+4-6-8+9+0-9+87=87
A = 87-4+6+8-9+9-87 = (87-87) +(9-9) +8+6-4 = 14-4 = 10
A= 10
A+4-6-8+9+0-9+87=87
A+4-6-8+9+0-9=87-87
A+4-6-8+9+0-9=0
A+4-6-8+9+0=0+9
A+4-6-8+9+0=9
A+4-6-8+9=9-0
A+4-6-8+9=9
A+4-6-8=9-9
A+4-6-8=0
A+4-6=0+8
A+4-6=8
A+4=8+6
A+4=14
A=14-4
A=10
Verificare
10+4-6-8+9+0-9+87=
=14-6-8+9+0-9+87
=8-8+9+0-9+87
=0+9+0-9+87
=9+0-9+87
=9-9+87
=0+87
=87
A+4-6-8+9+0-9=87-87
A+4-6-8+9+0-9=0
A+4-6-8+9+0=0+9
A+4-6-8+9+0=9
A+4-6-8+9=9-0
A+4-6-8+9=9
A+4-6-8=9-9
A+4-6-8=0
A+4-6=0+8
A+4-6=8
A+4=8+6
A+4=14
A=14-4
A=10
Verificare
10+4-6-8+9+0-9+87=
=14-6-8+9+0-9+87
=8-8+9+0-9+87
=0+9+0-9+87
=9+0-9+87
=9-9+87
=0+87
=87