Question 987324
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H=hours worked, H > 40
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Gross=$8(40)+$12(H-40)
Taxable portion (Subtract untaxed first $80): $8(40)+$12(H-40)-$80
Deduct tax (25% tax means you get 75%):0.75($8(40)+$12(H-40)-$80)
Add Back untaxed $80 to get net:
Net=0.75($8(40)+$12(H-40)-$80)+$80 
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Simplify:
Net=0.75($320+$12H-$480-$80)+$80
Net=0.75($12H-$240)+$80
Net=$9H-$180+$80
Net=$9H-$100