\(v1=10=\frac{s1}{t1}\rightarrow t1=\frac{s1}{10};v2=16=\frac{s2}{t2}\rightarrow t2=\frac{s2}{16}\)
\(t2=0,5t1\rightarrow\frac{s2}{16}=0,5.\frac{s1}{10}\rightarrow s2=0,8s1\)
\(vtb=\frac{s1+s2}{t1+t2}=\frac{1,8s1}{1,5t1}=\frac{1,8}{1,5}v1=12\frac{m}{s}\)