Răspuns:
[tex]ex \: 4) \\ a) \frac{5}{2} = \frac{a}{4} - > a = \frac{5 \times 4}{2} \\ a = \frac{20}{2} - > a = 10 \\ b) \frac{b}{0.5} = \frac{3}{0.1} - > b = \frac{0.5 \times 3}{0.1} \\ b = \frac{1.5}{0.1} - > b = 15 \\ c) \frac{8}{c} = \frac{c}{3} - > \frac{8}{4} = \frac{6}{3} \: sau \: \frac{8}{2} = \frac{12}{3} [/tex]
[tex]ex \: 6) \\ a) \frac{3}{7} = \frac{a}{28} - > a = \frac{3 \times 28}{7} \\ a = \frac{84}{7} - > a = 12 \\ b) \frac{a}{2} = \frac{7}{3.5} - > a = \frac{2 \times 7}{3.5} \\ a = \frac{14}{3.5} - > a = 4 \\ c) \frac{4}{a} = \frac{a}{9} - > \frac{4}{2} = \frac{18}{9} \: sau \: \frac{4}{4} = \frac{9}{9} \\ d) \frac{0.6}{2 \times a} = \frac{0.9}{21} - > a = \frac{0.6 \times 21}{2 \times 0.9} \\ a = \frac{12.6}{1.8} - > a = 7 [/tex]
