Let x be the smaller and y be the largest number.
Since [tex]x+y=13[/tex], we deduce [tex]y=13-x[/tex]
Now, for the translation: "two more than the larger number" is [tex]y+2[/tex], while "twice the smaller" is [tex]2x[/tex]
Their sum is
[tex]y+2+2x[/tex]
And since we know that [tex]y=13-x[/tex], we have
[tex]y+2+2x = 13-x+2+2x = 15+x[/tex]