How many isosceles triangles with whole-number length sides have a perimeter of 20 units?

Thanks!

.  There are no 5-10-5 or 10-0-10 triangles!  Those are just 10 unti long lines!

Right. Triangles can't have a side length of 0, and 5-10-5 triangles do not satisfy the triangle inequality: https://www.mathsisfun.com/geometry/triangle-inequality-theorem.html