Answer:
-21
Step-by-step explanation:
I assume this is a 2 by 2 matrix.

determinant = -5 * 4 - 1 * 1 = -20 - 1 = -21
So 7 is greater I am not smart I am just trying to answers some question
Old price: p1 = $ 3.90;
New price: p2 = $ 3.40.
The percentual decrease is given by
d(%) = [ (p2 - p1) / p1 ] * 100 %
d(%) = [ (3.40 - 3.90) / 3.90 ] * 100 %
d(%) = [ - 0.50 / 3.90 ] * 100 %
d(%) = - 0.128 * 100 %
d(%) = - 12.8 % (approximately)
So the price fell 12.8 % approximately.
I hope this helps. =)
Yes, 18 x 2 + 36, therefore the student was correct