Thrice the square of a natural number decreased by four times the number is equal to 50 more than the number. The number is :

Direction : What value should come in the place of question mark (?) in the following questions?

283 ÷25x4 + 186 = ? 

0.8% of a number is 31, then find the number.

Direction : What value should come in the place of question mark (?) in the following questions?

$$ 68\sqrt?-826=262 $$

Direction : What should come in place of the question (?) in the following question.

√(?) + 15² = 235

A is inversely proportional to square of B whereas directly proportional to C. Value of A was 27 when value of B was 4 and value of C was 6. Find the value of A when value of B will be 3 and value of C will be 8.

A man has eaten 100 grapes in 5 days. He eats 6 more grapes every day in comparison to the previous day. How many grapes did he eat on the first day?

What should be added to $$ {10 \ over 11} $$ to get the sum $$ {11 \ over 10} $$?