Sil vous plait aidez moi je ne comprend pas ...

A = 7/3 (6x+3) + 5/2 (4-2x)
42x/3 +21/3 + 20/2 -10x/2
42x/3 +21/3 +20/2 -10x/2
84x/6 +42/6 +60/6 -30x/6
50x/6 +102/6
B = 4(1-7y) + (4y -5)(y-1)
4 -28y + 4y² -4y -5y +5
+4y² -37y +9
3t(t+1) + ( 5 +t)(t -2)
3t² +3t + 5t -10 +t² -2t
4t² +6t -10
(4k -1)(9 + k) -9k (10 -3k)
+36k +4k²  -9 -k -90k +27k²
+31k² +55k -9
E = (m +2)(8 +3m) -2(1 -m)(m-7)
8m +3m² +16 +6m -2(m -7 -m² +7m)
14m +3m² +16 -2(8m -7 -m²)
14m +3m² +16 -16m +14 +2m²
5m² -2m +30