Answer:
a,c and d.
Step-by-step explanation:
a. [tex]\frac{d}{r}=t[/tex] is equal to
[tex]d=rt[/tex] multiplying both sides by r.
b . [tex]r=dt[/tex]
[tex]\frac{r}{d}=t[/tex] is different to [tex]\frac{d}{r}=t[/tex].
c. [tex]\frac{d}{t}=r[/tex] is equal to
[tex]d=rt[/tex] multiplying both sides by t.
d. [tex]\frac{d}{rt}=1[/tex] is equal to
[tex]d=rt[/tex] multiplying both sides by rt.