need help, thx in advance

In Module 2, we mentioned the use of the weak law of large numbers which tells us that the sample estimator will converge to the population parameter if we have sufficiently large number of observations (or sample size). In this question, we would like to see how big the sample size should be in order to get the approximation error down to a certain level. Assuming that we have a Binomial random varibale X ~ Bin(n, 0.8), what is the smallest sample size n such that P X - 0.8 > 0.1