Salutare!!
[tex] \bf 1999 \cdot 2000-1998 \cdot 1999-2 \cdot1998 = [/tex]
[tex] \bf 1999 \cdot (2000-1998) -2 \cdot1998 = [/tex]
[tex]\bf 1999 \cdot 2 -2 \cdot1998 = [/tex]
[tex]\bf 2 \cdot (1999 - 1998)= [/tex]
[tex]\bf 2 \cdot 1 = [/tex]
[tex] \boxed{\bf 2 }[/tex]
==pav38==