1/40÷4/5＋1/40÷1/5、
=1/40×5/4＋1/40×5
=1/40×(5/4＋5)
=1/40×25/4
=5/32
5/12÷1/8＋5/12÷7/8
=5/12×8＋5/12×8/7
=5/12×(8＋8/7)
=5/12×64/7
=80/21