How can I find the value of x given multiple Parallel Lines and multiple Transversals?

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Ive been given the following problem: enter image description here

I was unable to figure out how to solve the problem, and I was told the answer was the following; However, the program has failed to explain to me exactly how it got the answer... Looking online, I can only find solutions for single transversal, 2 line problems, which aren't necessarily difficult.. enter image description here

My question is, how exactly, piece by piece, do I find X given multiple transversals or parallel lines?

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With more parallel lines or transversals you just apply the "Parallel lines cut transversals into proportional segments." theorem for more than once. (This theorem is essentially Thales' Theorem.)

I created an example in the figure below. Since you had successfully obtained $x=5$ from the lower trapezoid, we can write the following for the upper trapezoid. $$\frac{y}{3}=\frac{10}{x}=\frac{10}{5}\implies y=6$$ enter image description here

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Just reduce the problem to the problem with two lines by passing a line parallel to one of your lines - for example (sorry for sloppy drawing):

enter image description here