Answer:
8.6 but im not sure.
Step-by-step explanation:
5 squared + 7 squared = 74 square root = 8.6
Answer:
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and 
use the second expression to calculate the left-hand side of the first equation:

Add 10 to both sides if this equation to get

and divide both sides by 2

this proves that x = 17, give the two initial equations