Urgent svp exercice 52.

a = -5/8  - -7/24 - 1/6
a = -5/8 +7/24 -1/6
a = -15/24 +7/24 -4/24
a = -19/24 +7/24
a = -12/24
a = - 1/2

b =4/5 + -2/3 +9/10 -5/6
b = 24/30 -20/30+27/30 -25/30
b = -45/30 +51/30
b = 6/30
b = 1/5