Bài $17:$
$a, \frac{3.5}{8.24}=\frac{15:3}{192:3}=\frac{5}{64}$
$b,\frac{2.14}{7.8}=\frac{28:28}{56:28}=\frac{1}{2}$
$c,\frac{3.7.11}{22.9}=\frac{231:33}{198:33}=\frac{7}{6}$
$d,\frac{8.5-8.2}{16}=\frac{40-16}{16}=\frac{24:8}{16:8}=\frac{3}{2}$
$e, \frac{11.4-11}{2-13}=\frac{44-11}{2-13}=\frac{33}{-11}=-3$
Bài$18:$
$a,20$ phút $=\frac{1}{3}$ giờ
$ b,35$phút $=\frac{7}{2}$ giờ
$c,90$ phút$=\frac{3}{20}$giờ
