i need help i don't understand #3

Answer:
I can't understand number 6 sorry :(
7. The DO side is the hypotenuese8.
8. 107.62
Step-by-step explanation:
The formula for this is:
[tex]a^2+ b^2 = c^2[/tex]
66 × 66 = 4,356
85 × 85 = 7,225
4356 + 7225 = 11,581
[tex]\sqrt{11,581}[/tex] ≈ 107.62
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Have a great summer :)