Determine the system which is equivalent to the system:

Question

3x+4y=12
x-2y=9

a)
3x+4y=12
3x-6y=27

b)
3x+4y=12
2x-4y=18

c)
10y=-15
5x=30

d)
Any of A,B or C

Answer 1

In b, the first equation is unchanged.
In b, the second equation is multiplied by 2, every term, so it is unchanged.

Answer 2

In c, the values of x and y are explicit.
Substitute these values in A and B and see if they work.