cross-multiply

listen to the pronunciation of cross-multiply
Englisch - Türkisch
Clear an equation of fractions when each side consists of a fraction with a single denominator by multiplying the numerator of each side by the denominator of the other side and equating the two products obtained
Englisch - Englisch
To set the product of the extremes of a proportion equal to the product of its means

Cross-multiplying 3/5=x/2 yields 3\times2=5x.