${\mathrm{CH}}_3{\mathrm{C}}_6{\mathrm{H}}_5\underset{{\mathrm{H}}_2{\mathrm{SO}}_4}{\overset{{\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7}{\to }}\mathrm{Y}. \mathrm{Here} \mathrm{Y}$

 In this toluene reacts with potassium dichromate in acidic condition (which is a very strong oxidising agent which oxidises alkyl group to carboxylic acid group we 

will get benzoic acid as a product. Therefore,

${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{CH}}_3 \stackrel{{\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7/{\mathrm{H}}_2{\mathrm{SO}}_4}{\to }{\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH}$