thnx i fixed it, i had a typo in my code.

i had:

matrix.set(2, 0, nine);

matrix.set(2, 3, ten);

matrix.set(2, 3, eleven);

matrix.set(2, 3, twelve);

instead of

matrix.set(2, 0, nine);

matrix.set(2, 1, ten);

matrix.set(2, 2, eleven);

matrix.set(2, 3, twelve);