How can you use multiplication facts 1 and 2 to find 3 x 7?
The "multiplication facts" may be numbered differently in
different textbooks, so it is really hard to guess what
multiplication facts you are talking about. Better use the standard
names, for example, "commutative property", "associative property",
etc.
For a multiplication such as 3 x 7, you either memorize the
tables, your you do the repeated addition (3 x 7 = 7 + 7 + 7, that
is, 7 appears 3 times as an addend.)