Can anyone help me with this please

1270 J

Explanation:

Recall that the mechanical energy of a system is the addition of the Potential energy and the Kinetic energy at any given time.

As the skier descends, potential energy is converted into kinetic energy, but the total mechanical energy should remain the same.

We see that it is not the case, so that difference is what has gone into thermal energy;  19500 J - 18230 J = 1270 J

glass has been rated on the mohs scale as 5.5

divide the right side by the left side

0.024÷1.2=0.02 for example