Since we don't have a figure we'll assume one of them is right and we're just being asked to check if they're the same number. I like writing polar coordinates with a P in front to remind me.
It's surely false if that's really a 3π/7; I'll guess that's a typo that's really 3π/4.
P(6√2, 7π/4) = ( 6√2 cos 7π/4, 6√2 sin 7π/4 )
P(-6√2, 3π/4) = ( -6√2 cos 3π/4, -6√2 sin 3π/4 )
That's true since when we add pi to an angle it negates both the sine and the cosine,
cos(7π/4) = cos(π + 3π/4) = -cos(3π/4)
sin(7π/4) = sin(π + 3π/4) = -sin(3π/4)
Answer: TRUE