So when you're adding consecutive numbers like this. 1+2+3...+39. You add 39 and 1. This is 40. 2+38 is 40. This is a pattern. Now, we do 40 multiplied by 39 and this will give you the number 1620. After this you would have to divide this product by 2. The answer will soon be 780.
Three side lengths that meet the requirements of the triangle inequality will form exactly one triangle.
_____
The triangle inequality requires the sum of the short sides be at least as long as the long side. Here, we have 3 + 4.69 = 7.69 > 7, so we satisfy the triangle inequality.
The side lengths can be arranged in clockwise or counterclockwise order, least to greatest. Each triangle is a reflection of the other, so they are considered to be the same triangle (congruent).
