aider moi pour le n° 84 svp

a. (2×+3×)(3x+8)
=2×x3×+2×x8+3x3×+3x8
=6ײ+16×+9x+24
=6ײ+24×+24

b. (1+2×)(9×-4)
=1x9×+1x(-4)+2×x9×x(-4)
=9×-4+18ײ+8×
=18ײ+×-4

c.(7-4)(6×-5)
=7x6×+7x-5+(-4×)x6×+(-4×)x(-5)
=42×+(-35)-24ײ+20×
=-24ײ+62-35