Write a equation of the line that passes through (2,1) and has a slope of 3

My math teacher told my class to "steal" a 6th grade fraction word problem from the internet, word problems? : -p requirements: only a 1 step word problem. needs to be complex.

Solve for x and y: 217x + 131y = 913; 131x + 217y = 827

Aclassmate thinks that solving a system by graphing gives an exact answer when the lines appear to cross at a grid point, but only an approximate answer when they don't. explain why this isn't true.