Решите пропорции: а) x:12=4 3/7:7 1/5; б) 6 1/2:x=6 5/6:4,1; в) 3 1/5:x=1,5:4 2/7; г) 3 7/19:1 1/2=2 3/5:0,8x.

\(x:12=\frac{31}{7}:\frac{36}{5}\).

\[x=12\cdot\frac{31}{7}\cdot\frac{5}{36}=\frac{155}{63}.\]

Ответ: \(x=\frac{155}{63}=2\frac{29}{63}\).

\(\frac{13}{2}:x=\frac{41}{6}:4,1\).

\[x=\frac{13}{2}\cdot\frac{4,1}{\frac{41}{6}}=\frac{13}{2}\cdot\frac{41}{10}\cdot\frac{6}{41}=\frac{39}{10}=3,9.\]

Ответ: \(x=3,9\).

\(\frac{16}{5}:x=1,5:\frac{30}{7}\).

\[x=\frac{16}{5}\cdot\frac{30}{7}\cdot\frac{1}{1,5}=\frac{16}{5}\cdot\frac{30}{7}\cdot\frac{2}{3}=\frac{64}{7}=9\frac{1}{7}.\]

Ответ: \(x=\frac{64}{7}=9\frac{1}{7}\).

\(\frac{64}{19}:\frac{3}{2}=\frac{13}{5}:0,8x\).

\[0,8x=\frac{13}{5}\cdot\frac{3}{2}\cdot\frac{19}{64}=\frac{741}{640};\qquad x=\frac{741}{640}\cdot\frac{5}{4}=\frac{741}{512}.\]

Ответ: \(x=\frac{741}{512}=1\frac{229}{512}\).