Subtract 10/72 from 20/42, Solve 20/42

Subtract 10/72 from 20/42

20/42 - 10/72 is 85/252.

Find the least common denominator or LCM of the two denominators:
LCM of 42 and 72 is 504

Next, find the equivalent fraction of both fractional numbers with denominator 504
For the 1st fraction, since 42 × 12 = 504,
20/42 = 20 × 12/42 × 12 = 240/504
Likewise, for the 2nd fraction, since 72 × 7 = 504,
10/72 = 10 × 7/72 × 7 = 70/504
Subtract the two like fractions:
240/504 - 70/504 = 240 - 70/504 = 170/504
After reducing the fraction, the answer is 85/252

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