These equations arise from mathematical modelling and at this level usually but not always involve two unknowns. Students have done them at Level 1 and earlier.They can be easily solved using a good or graphical calculator, however as is often the case it is necessary to show working in order to get more than Achieved. Be sure to practise this sheet until you always get the problems on it right. It is a good idea to do equations which only have one variable. Do the sheet on this web site which are level 1 problems but also refer to the references below.
ESA MSG Level2 Ch171
ESA AME Level2 P6