Examine the following systems of equations. Decide for each system which method would be the most efficient, convenient, and accurate: graphing, substitution, elimination, or the equal values method.
Justify your reasons for choosing one strategy over the others. You do not have to solve the systems.

A.
x = - 2y + 6
x = 3 -4y

B
x = 4 - y
y = 3x + 4

C.
a + b = 10
3a -4a = 6