848:a ; 728:a ;608:a ;___:a ; ___:a ; x:a=31........=>
a) 848-728=120
728-608=120
608-120=488.....( al 4-lea nr.)
488-120=368.....( al 5-lea nr.)
368-120=248.....( al 6-lea nr.)
=> 248:a=31
a=248:31
a=8
b) (728:a)*(488:a) =?
(728:8)*(488:8)=
=91*61
=5551
c) 248-120=128 .....(numarul 7)
128-120= 8.........( numarul 8)
=> (488:8):(8:8)=
=61:1
=61..........=>....catul= 61