The answer is
.
Solution:
Use algebraic identity: 
For example: 
Given expression
and
.
To multiply these equations.




Combine like terms together.



Hence the answer is
.
Answer:
-24
Step-by-step explanation:
Easy way: 42 - 18 = 24, then translate it to negative 24 because your numbers are negative.
A little bit harder way: -42 + (-18) or -42 + 18 = -24