Dave weighs 175 pounds and can bench press three times his body weight, so he can bench press 175*3 = <<175*3=525>>525 pounds
Craig can only bench press 20% of Dave's 525 pounds, so Craig can bench press .20*525 = <<20*.01*525=105>>105 pounds
Craig bench presses 105 pounds and Mark does 50 pounds less than Craig, so Mark can only press 105-50 = <<105-50=55>>55 pounds
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