a+b+c=987
nr. pare consec.
a |----|
b |----|+2 }987
c |----|+2+2
987-2+2+2=981
981:3=324(a)
324+2=326(b)
326+2=328(c)
x+y+z=1719
nr. impare consec.
x|----|+1
y|----|+3 }1719
z|----|+5
(1719-9):3=1710:3=570(un nr. nat.)
570+1=571(x)
570+3=573(y)
570+5=575(z)