Question 972093
Last problem
There are 8 people in line.

x can stand in place 1,2,3,4, each with 1/8 probability.

in place 1, y has 4 places out of 7
in place 2, y has 3 places out of 7
in place 3, y has 2 places out of 7
in place 4, y has 1 place out of 7

This doesn't give the answer, because I assumed at least.  I assumed wrong.
For 3 people exactly, it is
place 1  (1/8) * (1/7) that y is in place 4
and place 2 the same for place 5
all the way to place 8 for x and place 5 for y
That is 8/56= 1/7

2.
60-65 2 SURVIVE, ONE doesn't.  (0.7)(0.4)(0.8)=0.224
60-70 2 survive, one doesn't   (0.7)(0.6)(0.2)=0.084
65-70 survive  (0.3)(0.4)(0.2)=0.024 
all survive  (0.7)(0.4)(0.2)=0.056
Add them to get 0.388

For the balls.
with replacement it is (5/12)(4/11)(3/10) (7/12)(6/11)(5/10)=
60/1320  * 210/1320=(1/22) (7/44) =7/968

without replacement
(5/12)(4/11)(3/10)(7/9)(6/8)(5/7)
= (60/1320) *(210/504)
=(1/22) (105/252)= (1/22)(35/84)=35/1848
=5/264