In math there are three main ways to solve two variable equations

they go about like so:

=there's this one called substitution and it goes about like this

=then there's combination that goes like this

=if you don't like those you can just go with graphing that goes like this

Some other sites are:

>>>they say purplemath is pretty good

>>>you could check out Ms. Felz'z site

>>>if you care you could find out the real reason for this site