The slope of the line, is the one with an variable, in this case x. The other value, 27.52, is the y intercept, which would represent how much money he began with. So the variable 17.63x represents how much he could expect to make per week. We know it is per week because there is only a single x, if there were two x's it would be per 2 weeks, three x's per 3 weeks and so on.
From this we can conclude the answer is B, Aidan can expect to save about $17.63 each week