Sorry wrong question
It involves a right triangle. If a length is missing in a right triangle, you can find it out by using the other two lengths.
Insufficient information. Is it a right triangle? And if so, which sides are the 7 and 3?
That depends on what is meant by length of AD but the 3 sides of an equilateral triangle are all equal in lengths.
The length of the third side depends on the opposite angle. If the angle is at or near zero, the length of the third side is at or near zero. If the angle is at or near 180 degree, the third side is just the sum of the other two sides, which is 10. So that third side has a range of 0 to 10 possible lengths.
It depends on what other information you have. Knowing the lengths of two sides of a triangle is not enough to calculate the third. You need to have some further information: and angle, the area, the length of an altitude or a median.
The length of the hypotenuse of a right triangle with legs of lengths 6 and 8 is: 10
The length of the hypotenuse of a right triangle with legs of lengths 5 and 12 units is: 13The length of a hypotenuse of a right triangle with legs with lengths of 5 and 12 is: 13
A triangle with no equal side lengths is a scalene triangle.
An EQUILATERAL triangle has all three sides the same length. An ISOSCELES triangle has two sides with the same length. A SCALENE triangle has all three sides different lengths.
The length of the hypotenuse of a right triangle with legs of lengths 6 and 8 inches is: 10 inches.
It all depends on what information you DO have. If all you have is two lengths, then all you can say is that the missing side is greater than the difference between the two and less than the sum of the two.