The question is ambiguous. If the expression is 3√(x-1)/√(x-1), then the limit is 3 because the factor √(x-1) cancels out. In all other interpretations of the expression the limit is infinity.
Other interpretations: 3√(x-1)/(√x - 1), (3√x -1)/√(x-1), (3√x - 1)/(√x - 1).