18x+4y= -16

9x+7y=17



a

Multiply 1st equation by __ to set up eliminating x by addition.


b

Multiply 2nd equation by __ to set up eliminating x by addition.


c

Multiply 1st equation by __ to set up eliminating y by addition.


d

Multiply 2nd equation by __ to set up eliminating y by addition.