$11\cdot 18=\left(10+1\right)\cdot 18=180+18=\underline{\underline{198}}$

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$11\cdot 23=\left(10+1\right)\cdot 23=230+23=\underline{\underline{253}}$

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$11\cdot 38=\left(10+1\right)\cdot 38=380+38=\underline{\underline{418}}$