Whats the equation and answer for these two separate questions

Answer:
1).
[tex]speed = \frac{distance}{time} \\ speed = \frac{100}{4} \\ speed = 25 {ms}^{ - 1} [/tex]
2).
[tex]time = \frac{distance}{speed} \\ time = \frac{225}{75} \\ time = 3 \: s[/tex]