Question

what is the value of b11?

Answer 1

since Matrix A is added with Matrix B
then each component must be added to its corresponding component
a11+b11=0
a11=-b11
if
a11*b11=-16
then a11=+4 and b11=-4 or a11=-4 and b11=4
a11 is postive so our answer should be
a11=4 and b11=-4