Question

Find the solution 2x+5y=12

Answer 1

You can draw a graph of that equation.  When you do that, the graph is a
straight line, and EVERY POINT on the line is a solution of the equation. 
There are an infinite number of them.

You can find as many of them as you want.  Pick any number you like
out of the air, and call it 'x'.  Now find the number that's 2.4 more than
negative 0.4 of  'x' and that's 'y'.  Together they form one solution to
the equation.