when dealing with balance equations you always ask yourself how much do you have on the left side and how much you have on the right side. for example CaCO3-(lets pretend that an arrow ) CaO + CO2 this is the equation of thermal decomposition of limestone . btw so that one is already balanced butt you see how on the left side you have only one calcium and you have one carbon and three oxygen and then after the arrows you have again one calcium and one carbon and three oxygens one combine with calcium and two with carbon . something what helps me a lot when dealing with balancing equations is to wright what i don't have and have like this left side Ca=1, C=1 etc.. do that with pencil and the atoms that you don't have the same amounts on both sides you balance it . remember big numbers in front means multiplies by anything that comes after and small number bellow an metal or compound means that it only applies to that compound .if that dint help try watching videos on the topic and topics you mostly struggle with . go to your exam board website look for past papers and go straight to 6 mark questions and open your revision guide and answer them on you text book . after you answer check if it fits the necessary criteria and revise you answer . you don't have much time now so i suggest to read and do 6 marks questions those are the ones that change C to B , B to A . belive in yourself don't overthink it . yes its trues you should have started earlier but now you don't have time to play victim . and good luck