Solving systems of equations in three variables

Bugs bunny was 33 meters below ground, digging his way toward pismo beach, when he realized he wanted to be above ground. he turned and dug through the dirt diagonally for 80 meters until he was above ground

Jamie went to home depot.she bought 25 bags of soil that cost $9 per bag.she bought 15 pots at $8 each, and she bought 23 bags of pebbles at $15 each.she used a coupon that gave her $5 off for every 100 dollars she spent. how much did jamie pay at the end?

What is the missing step in this proof ?