please help me fill this out thanks

Answer:
7 mm
Step-by-step explanation:
[tex] \frac{7 \sqrt{2} }{ \sin(90) } = \frac{j}{ \sin(45) } \\ \frac{7 \sqrt{2} }{1} = \frac{j}{ \frac{1}{2} \sqrt{2} } \\ j = 7 \sqrt{2} \times \frac{1}{2} \sqrt{2} \\ j = 7[/tex]