Hola Shirley
In this sentence from this exercise: "y el precio no es tan caro como puedas imaginar", this verb in the subjunctive is a "hypothetical poder", i.e. as you may/might imagine.
If the sentence said instead: "y el precio no es tan caro como puedes imaginar" -the use of indicative "como puedes" implies something that actually happens. It is as if the speaker is acknowledging the fact that the other person already thinks the price is not very high as opposed to being a hypothetical thought.
I hope this clarified it.
Saludos
Inma
