8b+[-[4a+2(7a-2b)]-3]
Multiply 2 by each term inside the parentheses.
8b-(4a+(14a-4b))-3
Since 4a and 14a are like terms, add 14a to 4a to get 18a.
8b-(18a-4b)-3
Multiply -1 by each term inside the parentheses.
8b+(-18a+4b)-3
Since 8b and 4b are like terms, add 4b to 8b to get 12b.
12b-18a-3
or -18a+12b-3