Solution:

On multiplying all the 6 pairs we get (a*b*c*d)^3.
Assuming the missing product is a*b, then amid the 5 given products we see (a*c)*(b*d)=(a*d)*(b*c)
If we look at the numbers clearly 5 is out of the equation because there is nothing to balance it so the only remaining match is 2*6=3*4, so a*b*c*d=2*6=12.
So the product of all 6 pairs should be 12^3, the product of the given 5 is 720, so the missing one is 12/5=2.4

Solution:

XIX is the answer which refers to nineteen in roman numeric system. On taking out one i.e. I, we will get XX that is equal to twenty.

Solution:

41 years.

If the current age of Dakota is x
4(x+4) + 4(x+5) = 10x
Thus x=41 years

Solution:

99 matches.

The number of matches will always sum up to one less than the number of players in a knock out tournament. You may calculate it in any manner. Thus 99 matches were played.

Solution:

The answer is 0.
As
6 / 7 = 42 but the answer is written as 2
3 / 9 = 27 but the answer is written as 7
8 / 2 = 16 but the answer is written as 6
If we look at the answers, the second digit has been used in the problem.
Now, as
4 / 5 = 20 and the second digit is 0, the answer is 0.

Solution:

88 + 88/88

Solution:

fIvE thOUsAnd(5000)

Solution:

They can be expressed as the sum of the cubes of two different sets of numbers.

10^3 + 9^3 = 1729
and
12^3 + 1^3 = 1729

Solution:

There are six unique answers

Ans1:
7 x 4 = 28
36 / 4 = 9
1 + 4 = 5

Ans2:
9 x 4 = 36
28 / 4 = 7
1 + 4 = 5

Ans3:
3 x 8 = 24
56 / 8 = 7
1 + 8 = 9

Ans4:
7 x 8 = 56
24 / 8 = 3
1 + 8 = 9

Ans5:
4 x 8 = 32
56 / 8 = 7
1 + 8 = 9

Ans6:
7 x 8 = 56
32 / 8 = 4
1 + 8 = 9

Solution:

10 miles