Question 6: D
Question 7: B
K= (5a+3) (3a-2)
K= 5a× 3a+5a× (-2) +3×3a+3×(-2)
K= 15a²-10a+9a-6
K= 15a²-a-6
Question 8: D
L= (7-b)×7
L= 7×7+7×(-b)
L= 49-7b
