Book Maths Puzzle

A can copy 50 papers in 10 hrs while A &B together can copy 70 papers in 10 hrs.how many hrs will be required for B to copy 26 papers?

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Book Other Question

9
3 4
1 5 16
? 14 7 23
This one is a little more difficult because you are not told if the object is heavier or lighter.

You have 9 gold coins. All 9 coins look exactly the same but one coin is a fake and is either lighter or heavier than the other 8 coins. You have a scale - balance type with 2 trays - but can only load it twice. How do you find the fake gold coin?