Solutions by everydaycalculation.com

790 - 721 is -2390.

- Find the least common denominator or LCM of the two denominators:

LCM of 90 and 21 is**630**

Next, find the equivalent fraction of both fractional numbers with denominator 630 - For the 1st fraction, since 90 × 7 = 630,

790 = 7 × 790 × 7 = 49630 - Likewise, for the 2nd fraction, since 21 × 30 = 630,

721 = 7 × 3021 × 30 = 210630 - Subtract the two like fractions:

49630 - 210630 = 49 - 210630 = -161630 - After reducing the fraction, the answer is -2390

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