4/5÷8-4/15×1/8
=4/5 x1/8 -4/15 x1/8
=(4/5-4/15)x1/8
=8/12 x 1/8
=1/12
3÷6/7÷7/9
=3x7/6x9/7
=3x(7/6x9/7)
=3x3/2
=9/2