I've tried to simplify the following example as much as possible for ease of reading...
A manufacturer finds that for a new model, at £240 a unit, 20 units per week are sold. However, during promotion, the model was priced at £160 per unit, 45 units per week were sold. Let S be number of units sold per week, and X (in GBP) be the price of a unit. All production is sold.
How do I show that, for value of the price X, the number sold S is given
by the linear function:
S = 95 - (5/16)X
Any help much appreciated, Thank you.