15,17,19 are all odd numbers and add to 51
Swapping rows alters the sign of the determinant:

Multiplying a single row by a scalar scales the determinant by the same amount:

Then

Divide 4 on both sides. and the answer is X= -7
No
if it has 1 acute angle, then the other 2 must be more than 90 each in other words, the other 2 angles must be over 180
all angles add to 180 no more
so no is answer