Hi.. I'm following along in a book for my Discrete Mathematics class and I'm having trouble finding out what's going on between two steps algebraically.
21-1(77-3 x 21)
= 4 x 21 - 1 x 77
Exactly what is happening between these two steps? I can't see where the 4 comes from.
(Note: The xs in this problem stand for multiplication, not a variable x)