Find the value of "a" if the deteminant of

(6 3)
(4 a)IS:

a)6 b)3 c)0 d)-12

(the matrix is six above and four below,three above and "a" below)

the determinant of your matrix is

6a - 12

to solve for a we must know what that is equal to.
Are the choices you give possible answers for a? If so, you don't have enough information
Are the choices you give the value of the determinants? Then you have 4 different questions and I will do the first one

for a) 6a-12 = 6
6a = 18
a = 3

do the others the same way.