Ex 2et 4 merci besoin de votre aide

bonjour,

a = 3/7 - 9/14 +7/2 = 6/14 -9/14 +49/14 = 55/14-9/14 =  46/14 = 23/7

b = 4/5 +3/5 x 3/2 = 4/5 +9/10 = 8/10+9/10 = 17/10

c = (1/4-4/3) x 5/8 = (3/12-16/12) x5/8 = -13/12 x 5/8 =-65/96

d =  7/3 x 2/11 : 5/15 = 7/3 x 2/11 : 1/3 = 7/3 x2/11 x3 = 7/3x3x2/11 = 7x2/11 = 14/11