Well we dont know what multiplies by 6 to get 300. So in this case we would have to first divide 300 by 6 to get our missing number.
300 ÷ 6 = 50
So 50 is our missing number.
If we wanted to check our work we would multiply 50 by 6
50 x 6 = 300
So this means our answer is correct.
Answer = 50
Good Luck! :)