Question 824992
{{{(matrix(3, 4, 1, -3, -5, -2,
                2, -5, -4, 5,
                2, 5, 4, 6))}}}
Now just do what it says:
{{{r[2]= -2r[1] + r[2]}}}
means: Replace row 2 with the sum of (-2 times row 1) and row 2.
{{{r[3]= -2r[1] + r[3]}}}
means: Replace row 3 with the sum of (-2 times row 1) and row 3.
{{{r[3]= 6r[2] + r[3]}}}
means: Replace row 3 with the sum of (6 times row 2) and row 3.