arrange 13 ,3`s in such a way there sum =100?

Answer 1

a) it can be done with four 3s:
(3/.3) x (3/.3) = 10 x 10 = 100

b) or with five 3s:
(33 x 3) + (3/3) = 99 + 1 = 100

c) or with six 3s:
(3+3) ! / ([(3^3) - 3] x .3) = 720 / 24 x .3 = 720 / 7.2 = 100

d) or with eight 3s:
(333/3) - (3/.3) - (3/3) = 111 - 10 - 1 = 100
or
(3333/33) - (3/3) = 101 - 1 = 100

Answer 2

Seven 13s and three 3s!

Answer 3

If only the + sign is allowed, it is impossible. You should be more specific about the rules.