Răspuns:
Explicație pas cu pas:
( 7/3) : ( 28/5) = ( 15/4) : x
( 7/3 ) × ( 5/28) = ( 15/4) × ( 1/x)
(7/28) × ( 5/3) = 15/4x
15/4x = 5/(4×3) produsul mezilor = produsul extremilor
5 × 4x = 15 × 12 ║ : 5 × 4
x = 3 × 3
x = 9
7/3 : 28/5 = 15/4 : x
7/3 * 5/28 = 15/4 : x
5/12 = 15/4 : x
x = 15/4 : 5/12 = 15/4 * 12/5 = 9
