vite aider moi svp a rendre demain

bonjour

A = ( 1/4 - 1/5) x ( 7 - 37/9)
A = ( 5/20 - 4/20) x ( 63/9 - 37/9)
a = 1/20 x 26/9
A = 26/180 = 13/90


B = ( 2 - 1/3) : ( 3 + 1/4)
B = ( 6/3 - 1/3) : ( 12/4 + 1/4)
b = 5/3 : 13/4
b = 5/3 x 4/13 = 20/39

C = 54 x 10 ⁸ sur 9 x 10²
c = 6 x 10 ⁶

d = 16.8 x 10 ⁵ sur 420 x 10 ⁷
d = 0,04 x 10 ⁻²
d = 4 x 10 ⁻⁴