It is very simple, all you have to do is add three to x every time, for example if x is 153, y will be 156. 3 should be the beginning, the y intercept in graphs, and the beginning means x should be 0.
since there is no table included with the question I'm concluding that you need to find values of y using values of x, simply substitute the x values in the equation and you'll get the y value like this
