Total distance traveled = 4 + 6 = 10 miles
Total time = 15 + 25 = 40 minutes
Speed = 10 miles ÷ 40 minutes = 0.25 mph
 
        
                    
             
        
        
        
The degree of a polynomial is the highest power of its terms. 
The power of a term is the sum of the powers of all the variables in a term.
A polynomial is written starting with the greatest power in standard form.
In the first case, the power of the first term is 3, the power of the second is 3 (2 from x + 1 from y) but the power of x has decreased so it is the second term, and then so on. 
In the second case, the power is starting form 2 and then increasing to 3. This is incorrect.
Therefore, Marcus' suggestion is correct.