Marcus has $$75$$ toy cars. $$\frac{1}{5}$$ of his toy cars are black, $$\frac{2}{15}$$ of the remainder are white, and the rest are grey. He hasmore black toy cars than white toy cars. 
Overseas Competition->Knowledge Point->Word Problem Modules->Solving Problems Involving Fractions and Percentages->Knowing the Base
$75\div5=15$ toy cars are black.  $15\times4=60$ toy cars are white or grey.  $60\div15\times2=8$ toy cars are white.  He has $15-8=7$ more black toy cars than white toy cars. 