For which operations is the set {–1, 0, 1} closed? choose all answers that are correct. a. addition b. division c. multiplication d. subtraction

Hello,

Addition : no because -1+(-1)=-2 not in set.
Division : no because 1/0 is not in the set :infinity
Multiplication yes:  {-1,0,1}*{-1,0,1}={-1,0,1}
Substraction: No because (-1)-(1)=-2 not in set.

Answer C

On monday,mrs.wise bought 3 lbs of apples at $4per lb= 4*3=$12on tuesday ,20%off and she buy 5 lbs of apples = $4-20%=3.20*5lb=$16example: other wise when she buy 5lbs on monday she have to spend 4*5=20