coucou quelle est la valeur de X ?? 5X+12=2X-9 6(3X-7)=13-(8X-5)

5x+12 = 2x-9
5x-2x = -9 + (-12)
3x = -21
x = -21/3 = -7
6(3x-7) = 13 -(8x-5)
18x-42 = 13+8x+5
18x-8x =13+5+42
10x = 60
x = 6

c est la premiere reponsse 5x+12=2x-9