Answer:
Infinitive phrases include infinitives. ... Examples include, “to walk,” “to read,” or “to eat.” Infinitives can act as nouns, adjectives, or adverbs. As a noun, they might act as the subject of the sentence. For example, “To travel is the only thing on her mind.” As an adjective, they'll modify a noun.
Explanation:
N = # pounds
$1.65 = price per pound
grapes cost

When you multiply cost/pound by the number of pounds, the result is the cost for however much of the grapes Ryan buys.
Therefore,
m = 1.65n
Maybe you have to check yourself and see where the need of improvement is needed.