We have:
[tex]\frac{5}{2}x\text{ and }\frac{5x}{2}[/tex]These fractions are equal because the x is found by multiplying and it is as if we have this:
[tex]\frac{5}{2}\times\frac{x}{1}\text{ and }\frac{5\times x}{2}[/tex]And as we already know:
[tex]\frac{5}{2}\times\frac{x}{1}=\frac{5\times x}{2\times1}=\frac{5\times x}{2}=\frac{5x}{2}[/tex]