Answer:
See attached worksheet
Explanation:
Deciding on "more efficient" involves judgement. The first set of equations is easily solved with substitution, since we already have the value of x (2). Just enter 2 for x in the second equation to find y. The rest have solutions that can be found after adding or subtracting one equation from the other, after multiply one by a factor that will result in the elimination of either the x or y after the equations are combined. Use the answer (for x or y) to find the other value (y or x)