Svp merciii bcpppppp

Explications étape par étape:
A) (5÷8)×(3÷10) = 15÷80 = environ 0.19
(21÷8)-0.19 = 2,435
B) (9÷10)×(5÷21) = 45÷210 = environ 0.21
(1÷2)+0.21 = 0.71
C) (5÷12)÷(10÷9) = 45÷120 = 0.375
(15÷4)+0.375 = 4,125
D) (9÷10)-(7÷10) = 2÷10 = 0.2
5×0.2 = 1