The chef lost 13% after trimming.
1) 100% - 13% = 87% left.
2) Change 87% to a decimal, 0.87
3) Multiply 80 × 0.87 = 69.6 lbs.
The chef then lost another 11% after cooking.
1) 100% - 11% = 89% left.
2) Change 89% to a decimal, 0.89
3) Multiply 69.6 × 0.89 = 61.94 or 62 lbs.
The chef would have about 62 pounds of trimmed, cooked strip loin left to serve his customers.