Hey :)
First, find the GCF.
It is 6 since it divides evenly into 42x and -18.
Second, factor out the gcf and divide each term by the GCF.
6(42x/6 - 18/6)
Lastly simplify.
6(7x-3)
There are many different ways to do it and that's one of them.
Hope this helps !!
Good luck:)
