Illustrated Commentary on Nine Chapters, Vol. 1

Multiply the denominator 3 from the right column by the numerator 2 from the left column representing 2/5 to obtain 6. Add these to obtain 11, which serves as the dividend. Multiply the denominators 3 and 5 from the right column to obtain 15, which serves as the divisor. If the dividend does not reach the divisor, use the divisor to name the remainder, resulting in 11/15. The question is answered.

Commentary says: Place 3, 7, and 9 the denominators in the right column, and 2, 4, and 5 the numerators in the left column. Multiply the denominator 7 from the right column by the numerator 2 from the left column, and further multiply by the denominator 9 from the right column part of the 2/3 calculation to obtain 126. Multiply the denominator 3 from the right column by the numerator 4 from the left column, and further multiply by the denominator 9 from the right column part of the 4/7 calculation to obtain 108. Multiply the denominator 3 from the right column by the numerator 5 from the left column, and further multiply by the denominator 7 from the right column part of the 5/9 calculation to obtain 105. Add these to obtain 339, which serves as the dividend. Multiply the denominators 3, 7, and 9 from the right column