You have an algebraic expression in which you are solving for x. When you are solving for a variable, you need to isolate it all alone. Since you are multiplying by 1/5, you will have to undo it by multiplying by its reciprocal. In this case you are multiplying both sides by 5/1.
5/1 *1/5x = 121*5/1
x = 605
To check your answer, plug this value in for x and multiply it by 1/5. You should arrive at 121! Good luck!