r=0 is the solution...
The equation 3m - 3m - 7 = 0, simplifies to -7 = 0 this means that the the solution is no solution, since -7 doesn't equal 0.
It's an equation in 'N' ... about the simplest one you could write.The solution of that equation is: N=0 .
x = 0
It is a linear equation in x. The equation has the solution x = 0.
Yes it is. The solution is: y=4 .
It has infinitely many solutions.
x = 0 and y = 4