Maths Problems, STUCK

[Numb3rs]

hey, i've had these two maths problems for a while and i've been pretty much stuck making no headway

Positive Integers are places in the vacant cells if the 5x5 grid below, such that each row and each column forms an arithmetic progression
A. Determine the number which must be placed in the cell marked *
B. If the Number 186 is removed, what is the smallest possible number which can be placed in the cell mark *

THere is a diagram below

And Two Gentlemen are having a duel about a disagreement. the rules for the duel are that each man is to arrive at the town hall at a random time between 6 and 7 am. if the other man is there then they duel, otherwise he waits 5 minutes. if after 5 minutes his opponent has not arrived he leaves with his honour intact
A. What is the probability that the duel will eventuate?
B. What is the shortest time they will need to wait in order to make a duel likely?

Could you please leave working out's as well so i understand the question

Thanks in Advance

 

[Denis]

Positive Integers are places in the vacant cells if the 5x5 grid below, such that each row and each column forms an arithmetic progression

052 082 112 142 172
039 074 109 144 179
026 066 106 146 186
013 058 103 148 193
000 050 100 150 200

That's the COMLETE grid; do whatever you need to do with it :wink: