Step-by-step Solution:

The probability of throwing a triplet is: \[ \left( \frac{1}{6} \right)^3 \times 6 = \frac{1}{36} \] The probability that a triplet is thrown in all three throws is: \[ \frac{1}{36} \times \frac{1}{36} \times \frac{1}{36} = \left( \frac{1}{36} \right)^3 \] The probability that a triplet is not thrown more than twice is: \[ 1 - \left( \frac{1}{36} \right)^3 \]