The height of the house = 10 m
Base of the ladder is 3 meters away from the house. So base = 3 m
Let us consider that it is a right angle triangle with one side 10 m and base is 3 m. So, we have to find the length of the ladder or the longest leg of the triangle. This can be found by Pythagoras theorem.
Pythagoras theorem is=


=

=

or a = 10.44
Hence, the length of the ladder is 10.44 meters.
Please find attached the image of the triangle. We have to find AC.