i din understand the wording of the question !
what does 500 is the multiple of the 100 closest to x mean ?
how do we translate it to get : 450 < X < 550
you have a number x and the closest number to it which is also a multiple of 100 is 500.
so for any number 450 < x < 550, 500 would be the colsest multiple of 100. for 450 colsest multiple of 100 would be 400 and for 551 it would be 600.