Answer:
see explanation
Step-by-step explanation:
Her error is in squaring (2y)²
She has (2y)² = 2y²
when it should be 2y × 2y = 4y²
Then
(2y)² = 6² + 8²
4y² = 36 + 64
4y² = 100 ( divide both sides by 4 )
y² = 25 ( take square root of both sides )
y = 
= 5
