we have that
f²{k^6/[k^4*k^3]}^-3
step 1
f²{k^6/[k^(4+3)]}^-3---------> f²{k^6/[k^7]}^-3-------> step 1 is correct
step 2
f²{k^6/[k^7]}^-3------> f²{k^(6-7)]}^-3----> f²{k^(-1)}^-3----> step 2 is correct
step 3
f²{k^(-1)}^-3------> f²{k^[(-1)*(-3)]}-----> f²{k^(3)}
therefore
Martha made a mistake in the step 3
the answer is
step 3
f²k³
