1) hard to graph by hand. Often you need a graphics calculator or a computer software like maple or matlab. Or the graph has to be given.
2) hard to tell the exact solution, just by observing point of intersection. for example if x = 2.8675, the viewer would say x= 3.
3) sometimes not easy to decide the axis window of y and x axis. For example if the solution is very large like x = 100000 and your graph ends at x = 100, you cannot see the solution
SUBSTITUTION CONS
1) Becomes tedious if a system has too many equations or variables
