Electron withdrawing group increases the positive charge and electron releasing group decreases the negative change. The degree of hydrolysis increases as the magnitude of positive charge on carbonyl group increases. Among these NO2 & CHO are electron withdrawing group from which NO2 has more −I effect than-CHO. On the other hand CH3 is a electron releasing group. Thus, the order of reactivity towards hydrolysis is 
Related Theory The mesomeric effect is negative (−M) when the substituent is an electron-withdrawing group and the effect is positive (+M) when the substituent is an electron donating group.