Question

Care este numarul necunoscut?
a+(20+30)=70
(50+20)+b=90
(80-10)-a=40
(90-70)-b=0.

Answer 1

a +50=70
a=70-50=20
70+b=90
b=90-70=20
70-a=40
a=70-40=30
20-b=0
b=20

Answer 2

a+[20+30]=70
a+50=70
a=70-50
a=20

[50+20]+b=90
70+b=90
b=90-70
b=20

[80-10]-a=40
70-a=40
a=70-40
a=30

[90-70]-b=0
20-b=0
b=20-0
b=20