If in a car race, the man who came two places in front of the last man finished one ahead of the man who came fifth, how many contestants were there?

To attend world science seminar, A famous chemist from Mexico visit
London. In the lab, the scientist was killed and his six assistants were under suspicion of killing the chemist.
Name of six assistants: Austin, Wayne, Dege, Oscaru, Lingard, and Rojo.
He left a note "76-20-44 79-16-22-7"

A local detective Jack was called to solve the case,

After reading the note, Jack instantly asked the police to arrest the murderers.

Who are the murderers?

Spot 5 differences in two Christmas tree below:

A famous swimmer can swim downstream in a lake in exactly 40 minutes with the lake current.
He can swim upstream in that lake in exactly 60 minutes against the lake current.
The length of the lake is 2 km.

How long he can cover the distance of one side at a still lake with no current?

What's the next in the series?

H, Be, F, S, Mn, Kr, In, Gd, Tl, ?

Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I am double, I am single,
I am black blue and grey,
I am read from both ends,
And the same either way.

If an electric train is travelling south, then which way is the smoke going?

What does below pictogram mean?

1 + 9 + 8 = ?
considering, 28 + 8 + 92 = 10

Solve below rebus puzzle?