The answer is C, hope this helps!
The mass of the rock in kg is 90,000 kg
Kx-3y=k
y=4x+1 ( we will put it in 1st equation )
kx - 3 (4x+1)=k
kx - 12 x - 3 =k
kx - 12 x = k+3
x(k-12) = k+3
x=

Also y=

We can not divide with zero.
k-12=0
k=12For k= 12 equations have no solutions.
Answer:
I found that it was -1, but everything online is telling me -36.