Question

If possible, determine the slope. 5 + 2x = 2 + 3x

Answer 1

This is not a straight line rather number line.

Answer 2

Equations with two variables produce graphs that are lines.  If the line on the graph
is straight, then it has one slope at every point on it.  If the line on the graph has any
curves in it, then it has different slopes at different points on it.  That's for equations
with two variables.

The equation in this question only has one variable, and it only produces a number . . . the number that 'x' must be in order to make the equation a true statement.  It's
not too hard to find:

5 + 2x = 2 + 3x

Subtract 2x from each side:

5 = 2 + x

Subtract 2 from each side:

3 = x

And that's it.  'x' is 3.

If you want to graph that, then what you get is a vertical line on the graph. 
It crosses the x-axis at the point where 'x' is 3 .

The slope of a vertical line is 'undefined', just like the slope of a brick wall. 
That means that some people would look at it and call it "infinity", but in real
math, it's just 'undefined' ... it has no name at all.