5x5 Question

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I'm just making sure, I understand that the 5x5 exercise weight should go up 5lb each week but should the 2 exercieses with the 2x8 that follow the 5X5 exercise go up?
Thanks

if you are completing more than 8 reps on both sets.

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Thanks
So I should pretty much fail on the last rep or 2 of the 2x8 exercises?
And
Am I *SUPPOSE* to lift the weight up every week on these exercies.
I don't really get the concept of the 2x8, could you guys please explain it for me.
Thanks heaps