I need the area of ABC but don't know how to get the base.

Base=Width x Length

if you are finding this for a triangle, then it is 1/2 Width x Length

From my viewpoint; your length is 4 and your width is 5, so your base should be 20 units

(sorry if this isn't complete; I was having some trouble understanding the full question)

introduction, methodology, results, discussion

step-by-step explanation:

an observational study is one which consists of actual observation to record data and then analyse the data.

there are a number of factors that should be analyzed before starting an observational study.

the main four factors are:

i) introduction:   this should be analysed to check whether the purpose of the study is correctly established and the data recorded are appropriate for the study

methodology:   the method of collecting the data, such as whether randomly selected, and whether sample size matches with the population to be studied, whether questions asked are easy to answer by common men, etc.

results: then results such as summary of data with comments should be studied thoroughly

discussion:   the last is the discussion, this can be either by management people or persons who are all interested , etc.

but which class are u may know that first