The total number of rooms is given as 260.
If Johnny wrote x + y = 260,
Then that means the single rooms were represented by y while the double rooms were represented by x. We know this because, the next equation shows
60x + 35y = 14000,
That is, x rooms at 60 dollars plus y rooms at 35 dollars equals to a total of 14000 dollars.
Therefore, we can solve Johnny's system of equations as follows;
![\begin{gathered} x+y=260---(1) \\ 60x+35y=14000---(2) \\ \text{From equation (1), let x=260-y} \\ \text{Substitute for the value of x into equation (2)} \\ 60(260-y)+35y=14000 \\ 15600-60y+35y=14000 \\ \text{Collect like terms;} \\ 15600-14000=60y-35y \\ 1600=25y \\ 64=y \\ \text{Next, substitute for the value of y into equation (1)} \\ x+y=260 \\ x+64=260 \\ x=260-64 \\ x=196 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/zpfe8cx8s2ycvxindrgr11k3ntnzevtm56.png)
That means 64 single rooms were rented out, while 196 double rooms were rented out and that resulted in a total sales of $14,000