Question

Answer 1

a =1/2+1/3=5/6

b: =4/5+1/4=16/20+5/20=21/20

Answer 2

\(a,\dfrac{25}{50}+\dfrac{5}{15}=\dfrac{25:25}{50:25}+\dfrac{5:5}{15:5}=\dfrac{1}{2}+\dfrac{1}{3}=\dfrac{1\times3}{2\times3}+\dfrac{1\times2}{3\times2}=\dfrac{3}{6}+\dfrac{2}{6}=\dfrac{5}{6}\)

\(b,\dfrac{72}{90}+\dfrac{7}{28}=\dfrac{72:18}{90:18}+\dfrac{7:7}{28:7}=\dfrac{4}{5}+\dfrac{1}{4}=\dfrac{4\times4}{5\times4}+\dfrac{1\times5}{4\times5}=\dfrac{16}{20}+\dfrac{5}{20}=\dfrac{21}{20}\)