Subtract a natural number from the denominator of the fraction (53/87), add the same natural number to the numerator, and the resulting fraction is (11/17), what is the natural number?
分数(53/87)的分母减去一个自然数，分子加上同一个自然数，所得的分数约分后是(11/17)，求这个自然数是多少．
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