6*4*5-100=20 50*9*2-80=820 2*7*25+150=500 15*9*4-540=0

Correct!

645 - 100 = 120 - 100 = 20

5092 - 80 = 900 - 80 = 820

2725 + 150 = 350 + 150 = 500

1594 - 540 = 540 - 540 = 0