Which of the following types of electromagnetic waves are not currently used in a,) x rays ,b,) radio waves, c)visible lights ,,d)

I think ,b,) radio waves

Make them both to where they have the denominator of 18that makes 3/2 equal 27/18 and 1/9 equal 2/18so now you have  27/18x+5=2/18subtract 5 from the other sideso now you have 27/18x+2/18-5then subtract 2/18 from 27/18 to get 25/18x=-5then divide 25/18 by -5 and your answer will be  -5/18