Question 347214
a)When {{{a=2}}} and {{{b=4}}}, the lines are identical and will have infinitely many solutions.
When {{{a=2}}} and {{{b<>4}}}, the line are parallel and will have no solution. 
For all other values of {{{a}}} and {{{b}}}, the lines will have a unique solution.
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b) {{{x+2y=6}}}
{{{2y=-x+6}}}
{{{highlight(y=-(x+6)/2)}}}