Question

34+45+120
34+512+19
715-(215+15)
316+(1516-58)

Answer 1

$frac{3}{4} + frac{4}{5} + frac{1}{20} = frac{3}{4} + frac{4}{5} + frac{1}{4*5}= frac{3*5}{4*5} + frac{4*4}{5*4} + frac{1}{4*5}= frac{15}{20} + frac{16}{20} + frac{1}{20}= frac{32}{20} = \ =frac{8}{5} =1 frac{3}{5} ; \ frac{3}{4}+ frac{5}{12}+ frac{1}{9}= frac{3}{4}+ frac{5}{4*3}+ frac{1}{3*3}= frac{3*9}{4*9}+ frac{5*3}{4*3*3}+ frac{1*4}{3*3*4}= \ = frac{27}{36}+ frac{15}{36}+ frac{4}{36}= frac{46}{36} = frac{23}{18}=1 frac{5}{18};$

$frac{7}{15}-( frac{2}{15} + frac{1}{5} )=frac{7}{15}-frac{2}{15} - frac{1}{5} = frac{5}{15} - frac{1}{5}=frac{5}{5*3} - frac{1*3}{5*3}=frac{5}{15} - frac{3}{15}= \ = frac{2}{15} ; \ frac{3}{16}+( frac{15}{16} - frac{5}{8} )=frac{3}{16}+ frac{15}{16} - frac{5}{8} = frac{18}{16} - frac{5}{8} =frac{18}{16} - frac{10}{16} = frac{8}{16}= frac{1}{2}$