4
1) We can notice that as far as the speed decreases the time to get home increases.
2) In addition to this, note that we can see that this is a constant behavior. Notice that the missing term is in the 4th row. And then we can continue the division picking the initial speed and the speed traveled:
[tex]\frac{60}{15}=4[/tex]
The same way we know that:
[tex]\begin{gathered} 60\div30=2 \\ 60\div20=3 \\ 60\div10=6 \end{gathered}[/tex]
3) Hence, the answer is 4
