# Maths

posted by
**Nouvuyo**
.

(a display of a goods in a store has to be organized in layers so that the 7th layer , from the floor, consist of 28 items while the 18th layer must have 6 items.the number of items in the different layers forms an arithmetic sequence.) (1) give the expression, in terms of a and d, for the 7th term and 18th term?