The basic idea of manipulating algebraic expressions is that they obey the same laws as arithmetic expressions. The following are some simple exercises along those lines. They ask you to enter numerical values for the variables $A$, $B$, $C$ ...
The expression $3(5-3 x)$ equals $Ax+B$
where $A$ equals:
and $B$ equals:
[NOTE: Your answers cannot be algebraic expressions.]