Explications étape par étape:
a) = (13 × 2)/(2 × 19) = 13/19
b) = (5 × 2)(2 ×3 ×7) = 5/21
c) = (3 × 2 × 7)/(2 × 5 × 3 × 5) = 7/25
d) = (3 × 7 × 11 × 5)/(11 × 3 × 2 × 7) = 5/2
