Let's plug in x = 3 to find out. So we just replace every copy of x with 3 and simplify both sides
-3(x-4) > 6(x-1)
-3(3-4) > 6(3-1)
-3(-1) > 6(2)
3 > 12
The last inequality 3 > 12 is false. So the first inequality is false when x = 3. So 3 is NOT in the solution set.
