let's look at this this way ...
multiply both sides of equation with 2 and you will have
do you see that nothing is changed ?
now with fractions ....
because of that under fraction is 2 (can be anything) to lose that fraction you multiply both sides with that whatever is under fraction ....
in this case multiply with 2
you don't multiply by two in your problem there... i just do that with my example to show you that nothing changes if you multiply both sides (or add or divide or ... ) Whatever is "down" in fraction (can't figure out how to write it on English ) you multiply both sides with THAT in your case it's 3x-7
so you will be free of the fraction
P.S. when multiplying fraction with number you don't multiply down expression
but only if you are multiplying fraction with fraction ...
you have solution in my first post (#2)
it's not problem for you with English ... it's mine
P.S. you need to get familiar with basic operations with fractions, and on fractions (as multiplying , divide, add , subtract .... ) so you will not have problem piking up stuff like this