An arithmetic progression (AP) has 18 terms. If the sum of the last four terms of the AP is 284. calculate the first term and the common difference
$284$ is a rectangle with sides $4$ and $71$. Notice, if you subtract a multiple of $3$ from $71$ to get the size of the first partition, your difference in $AP$ will become a multiple of $2$ accordingly.
$68+70+72+74=65+69+73+77=62+68+74+80 =\ ...\ = 284$
Since your first term of $AP$ is dependent on the common difference, your problem has many solutions.
From your Problem we get $$a_1+14d+a_1+15d+a_1+16d+a_1+17d=284$$ an equation in two unknowns.