a) \(\dfrac{3}{4}\) = \(\dfrac{3 \times 5}{4 \times 5}\) = \(\dfrac{15}{20}\);
\(\dfrac{2}{5}\) = \(\dfrac{2 \times 4}{5 \times 4}\) = \(\dfrac{8}{20}\);
b) \(\dfrac{5}{12}\) = \(\dfrac{5 \times 3}{12 \times 3}\) = \(\dfrac{15}{36}\);
Giữ nguyên phân số \(\dfrac{11}{36}.\)
c) \(\dfrac{2}{3}\) = \(\dfrac{2 \times 4 \times 5}{3 \times 4 \times5}\) = \(\dfrac{40}{60}\);
\(\dfrac{3}{4}\) = \(\dfrac{3 \times 3 \times 5}{4 \times 3 \times 5}\) = \(\dfrac{45}{60}\);
\(\dfrac{4}{5}\) = \(\dfrac{4 \times 3 \times 4}{5 \times 3 \times 4}\) = \(\dfrac{48}{60}\).