svp pour dm de maths merci

A = 7/2 - 3/4
   = 7×2/2×2 - 3/4
   = 14/4 - 3/4
   = 11/4

B = 4/7 + 2
   = 4/7 + 2/1
   = 4/7 + 2×7/1×7
   = 4/7 + 14/7
   = 18/7

C = 11/4 ÷ 7/18
   = 11/4 × 18/7
   = 11×18/4×7
   = 198/28
   = 198÷2/28÷2
  = 99/14

D = 24/36 × 9/27
   = 3×8×3×3/6×6×3×9
   = 8×3×3/6×6×9
   = 24×3/36×9
   = 72/324
   = 2×36/9×36
   = 2/9

E = 7/8 - 3/4 × 25/12
   = 7/8 - 3×25/4×12
   = 7/8 - 75/48
   = 7×6/8×6 - 75/48
   = 42/48 - 75/48
   = -33/48
   = -11×3/16×3
   = -11/16