Task 417

The task

Below is a magic square, meaning that the sum of the numbers in each row, in each column, and in each of the $2$ main diagonals are equal. What is the value of $n$? [asy]size(125); for(int i = 0; i<4; ++i) { draw((0,i)--(3,i),linewidth(1)); } for(int j = 0; j<4; ++j) { draw((j,0)--(j,3),linewidth(1)); } label("$n-3$",(.5,.5)); label("3",(.5,1.5)); label("$n+1$",(.5,2.5)); label("$n+2$",(1.5,.5)); label("$2n-9$",(1.5,1.5)); label("$1$",(1.5,2.5)); label("$2$",(2.5,.5)); label("$n$",(2.5,1.5)); label("$n-1$",(2.5,2.5)); [/asy]