a)
(-3/4 - 1/8 :3/4) : ( + 13/8)=
=(-3/4 - 1/8 ×4/3) × 8/13=
=(-3/4 - 1/6) × 8/13=
=(-9-2)/12 × 8/13=
=-11/12 × 8/13=
=-11/3 × 2/13=
=-22/39
b)
(1/1*2+1/2*3+.....+1/99*100) : [(3/5)⁴ * (3/5 )³ : (3/5)⁵ )]
=
=(1/1-1/2+1/2-1/3+.....+1/99-1/100) : [(3/5)⁷ : (3/5)⁵ )]
=
=(1/1-1/100) : (3/5)²
=
=99/100 ×25/9
=
=11/4