Which of the linear systems has exactly one solution

A: -x+y=9
x-y=9

B: -x+y=9
x-y= -9

C: -x+y=9
-x-y=9

D: x-y= -9
-x+y= -9

2 answers

find a system where the slopes are different. ANy two lines with different slopes intersect at exactly one point.

Looks like (C)
|1.5C-24|<=30