well, the difference from 5600 to 4200 is 1400.
If we take 5600 to be the 100%, how much is 1400 off of it in percentage?
[tex]\begin{array}{ccll} amount&\%\\ \cline{1-2} 5600&100\\ 1400&x \end{array}\implies \cfrac{5600}{1400}=\cfrac{100}{x}\implies 4=\cfrac{100}{x} \\\\\\ 4x=100\implies x=\cfrac{100}{4}\implies x=25[/tex]
