What is the value of x?

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x =

A20? -foot ladder is placed against a vertical wall of a? building, with the bottom of the ladder standing on level ground 19 feet from the base of the building. how high up the wall does the ladder? reach?

100 points, hi, i’m not sure what to do here,the data doesn’t seem to be quadratic .? can anyone me, in advance

Just tell me how to set up the equation.