D=diferenta
S=suma
S.I______I______I______I______I+40
D.I______I..........diferenta..............=>3*D+40
340=3*D+40
340-40=3D
300=3D
D=100
S=D+340
S=100+340
S=440
Acum stim si suma si diferenta numerelor .
a+b=440
a-b=100=>a=100+b
100+b+b=440
100+2b=440
2b=440-100
2b=340
b=340:2
b=170
a=100+b
a=100+170
a=270
Verificare : 270+170=440