yay help on the way

so what we do is we take 42and trun it to a deimalei then it now 0.42 then we have th find x so what you should do is is dived 210 bived by 0.42 then you get the answer and you put it like this x is eiled to 500 becaues if you take 0.42 nfr 210 you get 50...