Russia to west Africa distance travel via cargo ship

One of the main reasons societies settled along rivers in the neolithic era was because a) the village elders demanded it. b) the land there was more valuable. c) it was more safe and secure there. d) it provided irrigation for farming.

Solve for r in the formula v = ir, when i = 5 and v = 15.

What does 2[tex] {2}^{ - 4} \times {2}^{ - 2} [/tex]