Bonjour,
3/4 + 5/25 + 7/20
= (3 x 25) / (4 x 25) + (5 x 4) / (25 x 4) + (7 x 5) / (20 x 5)
= 75/100 + 20/100 + 35/100
= 130/100
= (10 x 13) / (10 x 10)
= 13/10
7/10 + 17/60 + 14/40 + 11/30
= (7 x 12) / (10 x 12) + (17 x 2) / (60 x 2) + (14 x 3) / (40 x 3) + (11 x 4) / (30 x 4)
= 84/120 + 34/120 + 42/120 + 44/120
= 204/120
= (12 x 17) / (12 x 10)
= 17/10.
