Bonjour,
a - b
7/3 - 10/21
= 49/21 - 10/21= 39/21 = 13/7
a*b
7/3 * 10/21
= 70/63 = 10/ 9
2a + b
2*7/3 + 10/21
= 14/3 + 10/21
98/21 +10/21 = 108/21 = 36/7
