Answer: 4x + 21 or 7 - 10x or -7x^2 - 3x + 7
not sure based on how the question is worded but it could be either 4x + 21 or 7 - 10x or -7x^2 - 3x + 7
Explanation:
option 1
7x + 3(7-x)
= 7x + 21 - 3x
= 4x + 21
option 2
7 - (7x + 3x)
= 7 - 10x
option 3
7- (x(7x + 3))
7 - (7x^2 + 3x)
-7x^2 - 3x + 7