GG easy mah dude
-8R1+R2 means take row 1, multiply it by -8 and add it to the 2nd row
-8R1=-8 -16 32 | 40
adding tat to the 2nd row we get
0 -10 37 | 42
so the resulting matrix is
[tex]\left[\begin{array}{ccc}1&2&-4 | -5\\0&-10&37 | 42\\-5&6&1 | 4\end{array}\right][/tex]
