bjr
29
-3 + qqch = 7
de tête tu trouves 10 puisque -3 + 10 = 7
mathématiquement
-3 + x = 7
tu veux x tout seul - donc on élimine - 3
-3 + 3 + x = 7 + 3
x = 10
5x = 19
5/5x = 19/5
x = 19/5
3x + 7x = 50
10x = 50
x = 50/10
x = 5
on a bien 3*5 + 7*5 = 15+35 = 50
x + 8 = 11
x + 8 - 8 = 11 - 8
x = 3
-2x = 9
-2x/(-2) = 9/(-2)
x = -9/2 = -4,5
et -4x + 9x = 45
5x = 45
5x/5= 45/5
x = 9