First of all, your English grammar needs as much help as your math! Spelling, capitalization, punctuation!
Let L=capacity of large bus and S = capacity of small bus.
L = S + 11
5L + 6S=495
Substitute
5(S+11) + 6S = 495
11S + 55= 495
Subtract 55 from each side
11S=440
You should be able to finish from here!