pouvez vous pour mon exos de maths svp

Exercice 1:

A = 7/18 + 3/18
A = (7 + 3)/18
A = 10/18
A = 5/9

B = -7/12 + 1/3
B = -7/12 + (1*4)/(3*4)
B = -7/12 + 4/12
B = (-7 + 4)/12
B = -3/12 = -1/4 (= -0,25)

C = 7/45 - 8/25
C = (7*5)/(45*5) - (8*9)/(25*9)
C = 35/225 - 72/225
C = (35-72)/225
C = -37/225

F = (-5-7) * (-3) + 4
F = -12*(-3) + 4 
F = 36 + 4
F = 40

Exercice 2:

D = 7X10^5 X 5 X 10^-9
D = 7X5 X 10^5 X 10^9
D = 35X10^5+(-9)
D = 35X10^5-9
D = 35X10^-4
D = 3,5X10^-3

E= (15X10^-2)/(25X10^-7)
E = 15/25 X 10^-2/10^-7
E = O,6X10^-2-(-7)
E= 0,6X10^-2+7
E= 0,6X10^5

Voilà, j'espère t'avoir aidé