We observe that the second equation of System B has had the x-term eliminated. That can be accomplished by adding 3 times the first equation to the second.
"To get System B, the <u> second </u> equation in System A was replaced by the sum of that equation and <u> 3 </u> times the <u> first </u> equation. The solution <u> is </u> the same as the solution to System A."
