Răspuns :
a-b=630
a=4xb
4xb-b=630
3xb=630
b=630:3
b=210
a=210x4=840
a-b=840-210=630
metoda grafica;
a-b=630
a=4xb
b /........../
a /........../.........../............/............./
a-b /_______630_______/
4 parti-1 parte=630
3 parti=630
1 parte=630:3=210
1 parte=b
b=210
a=4x210=840
a=840
a-b=840-210=630
a=4xb
4xb-b=630
3xb=630
b=630:3
b=210
a=210x4=840
a-b=840-210=630
metoda grafica;
a-b=630
a=4xb
b /........../
a /........../.........../............/............./
a-b /_______630_______/
4 parti-1 parte=630
3 parti=630
1 parte=630:3=210
1 parte=b
b=210
a=4x210=840
a=840
a-b=840-210=630