the only like-terms are on the right-hand-side, since the left-hand-side has only 1 term anyway.
[tex]\bf \cfrac{5}{2}s=\cfrac{3}{2}s+s\implies \cfrac{5}{2}s=\cfrac{3}{2}s+\cfrac{s}{1}\implies \cfrac{5}{2}s=\stackrel{\textit{using the LCD of 2}}{\cfrac{(1)3s+(2)s}{2}} \\\\\\ \cfrac{5}{2}s=\cfrac{3s+2s}{2}\implies \cfrac{5}{2}s = \cfrac{5}{2}s[/tex]