Ex 1:
2/5 x 4/5
Multiply both the numerators together and then multiply both the denominators together. You would multiply 2x4 which is 8 and 5x5 which is 25. Which leaves you with 8/25 and it will stay that way because you cannot simplify it further.
Ex 2:
2/5 and 5/3
Multiply across 2x5/5x3 and you end up with 10/15 which can be simplified/reduced to 2/3 because they share a common factor of 5.