Replace (x,y)=(1,1) into 3 equations, we have K = 9 & the relationship between C & T, P & P. In other words, the 3 equations equal:
(1) 3x + (C-3)y = C
(2) 9x + 12y = 21
(3) (R-15)x + 15y = R
These are all linear equations of 2 variables, so we can present them as lines on the coordinate plane.
These 3 lines already 1 shared point (1,1), so the question 'Is there any other solution?' = "Are these 3 actually just 1 same line?"
Statement 1: Replace C=7 into line (1) to find (1) & (2) is 1 line (let's call it l). Depend on R, (3) can be either l or another separate line crossing l at (1,1).
=> Insufficient
Statement 2: Replace R = 24 into line (3) to find (3) & (2) are 2 separate line regardless of (1). We can confidently answer No.
=> Sufficient
IMO BBunuel
\((K/3)x + Ty = C\)
\(Kx + 12y = 21\)
\(Px + 15y = R\)
\((x, y) = (1, 1)\) is a solution of the system shown above. Is there any other solution?
(1) \(C = 7\)
(2) \(R = 24\)