Problem parametrizing this matrix

Question

I have a system of equations:

$$x_1 + x_2 + 3x_3 − 2x_4 − x_5 = 1$$ $$5x_1 − 2x_2 + 3x_3 + 7x_4 + 8x_5 = 3,$$ $$−3x_1 − x_2 + 2x_3 + 7x_4 + 5x_5 = 2,$$ $$5x_1 + 3x_2 + x_3 − 2x_4 − 7x_5 = 3$$

With Gaussian elimination, I reach:

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How can I use parametrization to solve for x,x2...