How many weeks until all 350 rhinos disappear?

A very simple way to solve this specific problem is acknowledging the fact that the left hand side (L.H.S) is being multiplied by a factor of 10 to get the equation on the right hand side (R.H.S). So, if we multiply the denominator by 10, we'll get the answer, which would be 1 × 10 = 10 weeks.

Hope I could help! :)

because they could drop even lower..