Question 867099
Right triangle will have two legs.  One is a base and the other is a height.


Let b = base
Let y = height.


Formula for area of a triangle is {{{(1/2)b*y}}}.
Problem description is translated into symbols as ... you need to choose which length is the base and which is the height.


I will use "one leg" as b.
One leg is 6+y.
This means {{{b=6+y}}}.


Put this all into the equation for the given area.
{{{(1/2)by=260}}}
{{{(1/2)(y+6)y=260}}}
Now you should be no longer confused.  Solve for y and then use the found value to get the value for b.