After a fraction is reduced to 5 / 7 of the simplest fraction, it is known that the sum of the numerator and denominator of the original fraction is 72. What is the original fraction?

After a fraction is reduced to 5 / 7 of the simplest fraction, it is known that the sum of the numerator and denominator of the original fraction is 72. What is the original fraction?

211030352,
The molecular weight is 72 (7 + 5) × 5 = 30
The denominator is 72 (7 + 5) × 7 = 42
The score is 30 / 42

A fraction is reduced to five seventh of the simplest fraction. The product of numerator and denominator is 72
What's the original score?

There's something wrong with your question, because no matter how many times it is expanded, the product of numerator and denominator of 5 / 7 can't be 72?
1. The numerator and denominator are expanded several times at the same time: 72 (7 + 5) = 6
2. Original score: 5 / 7 = (5 × 6) / (7 × 6) = 30 / 42

Subtract the same number from the numerator and denominator at the same time. The new fraction is about two-thirds. What is the subtracted number?

Let this number be x, from the problem we can get (5-x) / (7-x) = 2 / 3, from the cross multiplication of numerator and denominator we can get 3 (5-x) = 2 (7-x), from the method of distribution we can get 15-3x = 14-2x, from the combination of similar terms we can get x = 1