To find f(g(x)), locate g(x) in the third column (labeled g(x)). Use that value as x in the first column, then read f(x) from the second column.
Example: f(g(1)) = f(2) = 1
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To find g(f(x)), locate f(x) in the second column (labeled f(x)). Use that value as x in the first column, and read the corresponding g(x) from the third column.
