Answer
Option B is correct.
Only the equation, 3x + 9 = 21, has a solution of x = 4.
Step-by-step explanation
We are told to pick the equation(s) with x = 4 as a solution from the equations,
5x - 8 = 44
3x + 9 = 21
4x = 24
x - 10 = -8
The step to solving this is to insert x = 4 and check if that is consistent with the given equation.
Option A
5x - 8 = 44
If x = 4
5(4) - 8 = 44
20 - 8 = 44
12 ≠ 44
Hence, this is not an answer
Option B
3x + 9 = 21
If x = 4
3(4) + 9 = 21
12 + 9 = 21
21 = 21
Hence, this is an answer for this question.
Option C
4x = 24
If x = 4
4(4) = 24
16 ≠ 24
Hence, this is not an answer to this question.
Option D
x - 10 = - 8
If x = 4
4 - 10 = -8
-6 ≠ -8
This is also not an answer to this question.
Hope this Helps!!!