Answer:
Option B: 6x-4=50; x=9 is the correct answer.
Explanation:
Given that:
x is the variable used for number.
6 times a number means 6x and difference means subtraction.
Thus according to given statement;
6x - 4 = 50
Adding 4 on both sides
6x - 4 + 4 = 50+4
6x = 54
Dividing both sides by 6

Hence,
Option B: 6x-4=50; x=9 is the correct answer.