Question

How do you solve this?

-3y + 2 [6 9] [27 -18]
[-12 15]=[30 6]

-3y + 2 [6 9]- [-6 -9] -3y + 2[0 0]
[-12 15] [12 -15] = [0 0]
-3y + 2 = [27 -18]= -3y [27*2 -18*2]
[30 6] [30*2 6*2]

-3y =[54 -36] -3y /-3[54/-3 -36/-3]
[60 8] = [60/-3 8/-3]

y = [-18 12]
[-20 -8/3]

Is this correct?

Answer 1

If I read it correctly, your dimensions are messed up. A 1x2 matrix * a 2x2 matrix yields a 1x2 matrix.

How can y be 2x2?

Take a look at this site, and you can enter your matrices using the sample notation.

http://www.wolframalpha.com/input/?i=2{6%2C9}*{{27%2C-18}%2C{-12%2C15}}-{30%2C6}