163又1/13÷41又1/39
=(164-12/13)÷(41+1/39)
=(164×39-12/13×39)÷(41×39+1)
=(164×(36+3)-36)÷((40+1)×(40-1)+1)
=(164×36+164×3-36)÷(1600-1+1)
=(163×3×12+41×4×3)÷1600
=((489+41)×12)÷1600
=530×12÷1600
=159/40