At the onset.. this sum looks challenging.. so much calculation.. Sometimes we need to modify the question. If you observe the denominators.. they are 2 4 5 10.. lets group them

then we can add numbers which have same denominator.. and then the sum becomes easy

So We need to look for clues in the question and re-organize the data to simplify the problem

Question 4

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Here are 5 cases.

14 x 5+5 =75

37 x 2 +1 =75

74 x 1 + 1 =75 ( The question didnt state that you can use the same digit again)

3 x 5 +60 =75

25 x 3 + 0 =75( The question didnt state that you cant use 0)

You can also use negative numbers. Did you get more cases?

Question 5

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Answer is 062

1. Take the fourth hint, 7,3,8 are incorrect.

2. Take the first hint, correct number is either 4 or 2 but not 8 as 8 is incorrect (as per the previous statement).

3.Take the second hint, 4 is not one of the correct numbers since in the first hint and the second hint, 4 is placed in the same position but in first hint, it says that 4 is well placed but in the second hint, it says that 4 is wrongly placed. So one of the correct numbers in the second hint will be 6. 1 will not be the correct number since it is not there in any of the options.

4.Take the third hint, 2 and 0 are the correct numbers but wrongly placed. 4 will not be the correct number (Given in 3rd step)

5. Take the last hint, 0 is the correct number but it is wrongly placed. From the 3rd hint and the 5th hint, 0 should be the first correct digit. From the 1st hint and the 3rd hint, 2 should be the last correct number. From this, 6 is the second correct number.