20+(7 1/3 - 6 7/8):3/4 - (5 1/4 - 4 21/40): 1 9/20

[latex]20+(7 frac{1}{3}-6 frac{7}{8} ): frac{3}{4} -(5 frac{1}{4}-4 frac{21}{40} ):1 frac{9}{20}= [/latex][latex]20+(7frac{40}{120} -6 frac{105}{120} ): frac{3}{4} -(5 frac{30}{120} -4 frac{63}{120} ): frac{29}{20} =[/latex][latex]20+ frac{55*4}{120*3} - frac{87*20}{120*29} =20+ frac{55}{90}- frac{3}{6}=20+ frac{55}{90} - frac{45}{90} =20+ frac{10}{90}= 20 frac{1}{9} [/latex]

1)7 1/3-6 7/8=7 8/24-6 21/24=6 32/24-6 21/24=11/242)5 1/4-4 21/40=5 10/40-4 21/40=4 50/40-4 21/40=29/403)11/24:3/4=11/24*4/3=11/184)29/40:1 9/20=29/40*20/29=1/25)20+11/18=20 11/186)20 11/18-1/2=20 11/18-9/18=20 2/18=20 1/9