Determine the growth rate for every 10years, from the following population;50,64,88,140,165 and 180.

since the ratio is not constant, just get the rate from first to last.

Assuming the table reflects 10-year increments,
(180/50) ^ (1/5) = 1.29
so, that's 29% on average, per 10-year period.
Or an annual growth rate of 1.29^0.1 = 1.026 or 2.6% per year