Q3 when graphing the equation we will face 3 cases
First when lines are intersecting at a point, then we can say that there's only one solution (intersected point)
2nd when lines are parallel to each other then they have no solutions.
3rd when lines are coincident to each other,they have infinitely many solutions.
Now, we can say that whenever two lines of an equation intersect they have solution and when they don't intersect they haven't any solution.
Q4 let length be 'l' and width be 'b' respectively.
l =12+b
Perimeter=2(l+b)=68
2(12+b+b)=68
12+2b=34
2b=22
b=11m
l=12+11
l=23m