Hi there, percentage change is just another name for percentage increase or decrease. So in this case. u want to find the percentage increase of carbon dioxide levels. To do this, you simply find the difference of the two levels of carbon dioxide divide by the original level of CO2 and times by 100 to give u a percentage. So u would do 2.05 - 1.62 = 0.42 then divide this by the original level (1.62) = 0.26543..... then times by 100 = 26.5% (1 decimal place) Hope this helped!
