Solution:
$136\ dollars$
Step by step solution:
Each kilogram of beef costs:
$(16 - 8): 2 = 4\ (dollars)$
The amount of dollars that Mr Lee had to pay for 7kg of crabs:
$16\times 7 = 112\ (dollars)$
The amount of dollars that Mr Lee had to pay for 6 kg of beef:
$4\times 6 = 24\ (dollars)$
The total amount paid by Mr Lee:
$112 + 24 = 136\ (dollars)$
Answer: $136\ dollars$