Construct a truth table with three inputs, A, F, and Bi and two outputs, D and Bo.
Think back to elementary subtraction facts:
A=1, F=1, Bi=0: With no borrow input, 1-1=0 and no borrow output. Right?
A=0, F=1, Bi=0: With no borrow input, 0-1=1 with the borrow output set.
A=1, F=0, Bi=1: With the borrow input set, 1-0-1=0 with no borrow output.
Determine the rest of the truth table entries.
Convert to two Karnaugh maps, one for each output. Follow the textbook's example for the full adder.