can anyone help me? again, im not really good at solving these things.

Answer:
[tex]\sqrt{14}[/tex]
Explanation:
The triangles are similar so ratios of corresponding sides are equal, that is
[tex]\frac{y}{2}[/tex] = [tex]\frac{7}{y}[/tex] ( cross- multiply )
y² = 14 ( take the square root of both sides )
y = [tex]\sqrt{14}[/tex]