Answer:
the marked answer is correct
Step-by-step explanation:
The desired end result is an identity matrix in the first three columns. The diagonal values are 1, as needed, so what remains is to eliminate the off-diagonal values. In row 2 that can be done by adding row 3 to it.
The next step should be to add rows 2 and 3 and replace row 2 with that sum.
Air energy
Heat energy
Kinetic energy
:-)
My guess is 30 mins sorry if wrong hope this helps