Stream cipher LFSR Known-Plaintext

Question

I am currently learning cryptography,

I got different tasks. The current one features stream ciphers based on LFSR which can be solved with the Gaussian algorithm. The cipher is: 0001 0010 01101101 I know that the first 8 bits of plaintext are all 1. The length of n is 4. So if I XOR them I get: 11101101 But now I am stuck and don't know how to translate it into a correct matrix.

1 1 1 0 | ?
1 1 0 1 | ?
1 0 1 1 | ?
0 1 1 0 | ?

Is this the correct way or do there only need to be 3 variables in front of the line? And where do I get the solution of the question marks from?

I hope someone can help me understanding cryptography. Thanks.