<u>ANSWER</u>
 is an example of literal equation.
 is an example of literal equation.
<u>EXPLANATION</u>
A literal equation is an equation in which letters or variables are used to represent real values.
A literal equation consists of at least two letters or variables.
The first option consists of two variables but it is not an equation. It is just an expression.
The second option is not a literal equation because it consists of only one variable. This is  just a linear equation in one variable. But a literal equation should have at least two variables or letters.
As for the third option, it does not even contain a variable or letter.
 
        
                    
             
        
        
        
Answer: Infinite
Step-by-step explanation:
We know that in a triangle the sum of all the interior angles must be 180°.
The given angles 50º, 90º and 40º
The sum of the angles 50º+ 90º + 40º= 180°
Thus, a triangle is possible with the given measurement.,
Let there is another triangle with the given angles, then by AAA similarity criteria they are similar.
Similarly, all the triangles with the same measurements of the angles must be similar.
Therefore, there are infinite number of triangles can be possible with angles measuring 50º, 90º, and 40º.