(a) Find the value of xif 10, x and 30 are in A. P. (b) If 6,x, y, and 18 are in A. P., find the value of x and y.

it's a optional mathematics Questions please solve him​

Anut store normally sells cashews for? $4.00 per pound and peanuts for? $1.50 per pound. but at the end of the month the peanuts had not sold? well, so, in order to sell 40 pounds of? peanuts, the manager decided to mix the 40 pounds of peanuts with some cashews and sell the mixture for $2.00 per pound. how many pounds of cashews should be mixed with the peanuts to ensure no change in the? profit?