Determine to which condition a vector is colinear to a given vector Algebra II

In which condition are \overrightarrow{u}=\dbinom{a}{4} and \overrightarrow{v}=\dbinom{3}{6} collinear ?

a=2

a=3

a=8

a=\dfrac{1}{2}

In which condition are \overrightarrow{u}=\dbinom{-3}{4} and \overrightarrow{v}=\dbinom{\dfrac{3}{2}}{a} collinear ?

a=-2

a=-\dfrac{9}{8}

a=8

a=\dfrac{1}{2}

In which condition are \overrightarrow{u}=\dbinom{a}{10} and \overrightarrow{v}=\dbinom{2}{5} collinear ?

a=4

a=3

a=2

a=\dfrac{1}{2}

In which condition are \overrightarrow{u}=\dbinom{a}{6} and \overrightarrow{v}=\dbinom{-5}{-10} collinear ?

a=3

a=5

a=-8

a=-7

In which condition are \overrightarrow{u}=\dbinom{a}{20} and \overrightarrow{v}=\dbinom{\dfrac{2}{5}}{5} collinear ?

a=\dfrac{8}{5}

a=\dfrac{3}{8}

a=\dfrac{1}{8}

a=\dfrac{1}{2}

In which condition are \overrightarrow{u}=\dbinom{a}{9} and \overrightarrow{v}=\dbinom{4}{-\dfrac{6}{7}} collinear ?

a=42

a=\dfrac{1}{42}

a=-\dfrac{1}{42}

In which condition are \overrightarrow{u}=\dbinom{a}{8} and \overrightarrow{v}=\dbinom{8}{32} collinear ?

a=2

a=4

a=\dfrac{1}{7}

a=\dfrac{1}{2}

In which condition are \overrightarrow{u}=\dbinom{a}{12} and \overrightarrow{v}=\dbinom{-\dfrac{24}{15}}{6} collinear ?

a=-\dfrac{48}{15}

a=-\dfrac{24}{15}

a=\dfrac{15}{12}

a=9