The example I would be using is the level of a see-saw and take
a point 1 /x of the way amid the middle and the left end. If you change
the point vertically by f feet, the far right finish transfers vertically
by f×−x feet. If you push down, f would be negative then you are
multiplying two negative numbers for a positive result, this means that the
other end moves up.
Given equation is y=2x+7 and 
Let's simplify the 2nd equation
before we can start graph so that calculation will be easy

multiply both sides by 2 to cancel out fractions

y=2x+7
which is exactly same as the first equatoin so graph of both will be exactly same and solution will be infinitely many solutions.
y=2x+7 has y-intercept 7 so first point will be (0,7). Slope is 2 so rise 2 unit up then 1 right and graph the new point.