Explicație pas cu pas:
a) a/3 = 5/8 → 8a = 5 × 3 → 8a = 15
a = 15/8
b) 5/a = b/9
ab = 5 × 9 = 45
45 - ab = 45 - 45 = 0
c) x/y = 2/5 ; y = 15
⇔ x/15 = 2/5
5x = 2 × 15
5x = 30 → x = 30 : 5 = 6
