1) 2 1/7 : (1,5a) = 5/14 : 0,8;

1) $2 \frac{1}{7} : (1,5a) = \frac{5}{14} : 0,8$ $\frac{15}{7} : (1,5a) = \frac{5}{14} : \frac{4}{5}$ $\frac{15}{7} \cdot \frac{1}{1,5a} = \frac{5}{14} \cdot \frac{5}{4}$ $\frac{10}{7a} = \frac{25}{56}$ $175a = 560$ $a = 3,2$ 2) $\frac{4,8}{1 \frac{7}{9}} = (1,2b) : 6 \frac{2}{3}$ $\frac{4,8}{16/9} = (1,2b) : \frac{20}{3}$ $2,7 = 1,2b \cdot \frac{3}{20}$ $2,7 = 0,18b$ $b = 15$ 3) $3,8 : (4c + 3) = 2 : 2 \frac{2}{19}$ $\frac{3,8}{4c + 3} = 2 : \frac{40}{19}$ $\frac{3,8}{4c + 3} = 0,95$ $4c + 3 = 4$ $c = 0,25$ 4) $\frac{0,3d - 1,5}{3 \frac{1}{3}} = 0,84 : \frac{7}{15}$ $\frac{0,3d - 1,5}{10/3} = \frac{21}{25} \cdot \frac{15}{7}$ $\frac{0,3d - 1,5}{10/3} = 1,8$ $0,3d - 1,5 = 6$ $0,3d = 7,5$ $d = 25$ 5) $\frac{3x - 1}{5} = \frac{x + 1}{3}$ $3(3x - 1) = 5(x + 1)$ $9x - 3 = 5x + 5$ $4x = 8$ $x = 2$ 6) $\frac{0,5y}{4} = \frac{y + 3}{8}$ Multiply both sides by 8: $2(0,5y) = y + 3$ $y = y + 3$ This equation has no solution.