How many syllables are in the line shall you compare thee to a summers day?

Let's break down the syllables in the line "Shall you compare thee to a summer's day?":

* Shall: 1 syllable

* You: 1 syllable

* Com-pare: 2 syllables

* Thee: 1 syllable

* To: 1 syllable

* A: 1 syllable

* Sum-mer's: 2 syllables

* Day: 1 syllable

Adding them up, we have 1 + 1 + 2 + 1 + 1 + 1 + 2 + 1 = 10 syllables.