calculer: 7|8-3|4×20|9

7/8 - 3/4 x 20/9
= 7/8 - (3 x 20)/(4 x 9)
= 7/8 - 60/36
= (7 x 36)/(8 x 36) - (60 x 8)/(36 x 8)
= 252/288 - 480/288
= - 228/288
= - (12 x 19)/(12 x 24)
= - 19/24