In matrix multiplication you multiply the elements of rows in the first matrix with elements of columns in the second matrix. If you want total sales, you will want to multiply the number of tickets sold times the price of the tickets. These will need to be the rows of the first and colums of the second matrices.

As with any matrix multiplication, the number of columns in the first matrix must be the same as the number of rows in the second matrix. That resultant matrix will have the same number of rows as the first matrix and the same number of columns as the second matrix. For example, multiplying a 2x3 matrix with a 3x4 matrix is possible and will result in a 2x4 matrix. I don't see how you can do this problem with a resultant matrix that ends up being 3x1. A 3x3 matrix is more likely, but the only numbers in the resultant with any meaning will be on the diagonal (this is 3 numbers like in a 3x1 matrix).

Set up the matrices and keep track of what each number is. For each theme park (row of the first matrix) you will want to add up the sales (per ticket will be the colums of the second matrix - which will be totals once you have multiplied). Keep track of which park's income is going into each sum in the resultant matrix and you'll hopefully see why only the numbers on the diagonal are meaningful.