Congruence means two objects (whether two dimensional or three dimensional) are identical in size and shape. Everything about them -- their angles, lengths of sides, overall dimensions -- are identical. Similar means being the same shape. Two congruent figures must be the same shape, so they are similar.
Gemma was hiking for 2 1/2 a hour for 3 hours so u have to multiply 2.5 by 3 and that gonna equal 7.5 so u leave that alone and come back to it later so u get 11 3/8 minus 7.5 and it gonna equal 3 7/8 and I hope that helped you