4/5x99+4/5
=4/5×(99+1)
=4/5×100
=80
24x(2/3+1/6-3/8)
=24×2/3+24×1/6-24×3/8
=16+4-9
=11
(5/9-1/6)÷(7/8+1/3)
=(7/18)÷(29/24)
=7/18×24/29
=28/87
2x5/9+4/9
=10/9+4/9
=14/9