System of equations coding problems

Hi, I'm new to Matlab and I was wondering if anyone can lead in the right direction for the solving a system of equations like the second array pictured? I've solved the first one but i'm stuck on the second. Thanks

Answer 1

[Star Strider]

See the documentation on mldivide,\ (link).

Answer 2

[Torsten]

n = 10;
A = full(gallery('tridiag',n,1,2,3));