Final answer:
Compound adjectives are formed by combining two or more words to describe a noun. In this case, hyphens are needed in the compound adjectives 'small house,' 'middle-class neighborhood,' and 'much-needed addition.'
Step-by-step explanation:
Mason could only afford a small house in a middle-class neighborhood, but he's planning to build a much-needed addition, which will expand the house to 1,500 square feet.
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