The variable z varies jointly with x and y. if z = 18 when x = 2 and y = 6, find the constant of variation, k, and then find the value of z when x = −4 and y = 5.

the constant of variation k is
the value of z is

Atemperature of 1.64◦f corresponds to answer in units of ◦c.

Asap! i'm not good math and i'm lost.

Someone answer asap for ! a discount store’s prices are 25% lower than department store prices. the function c(x) = 0.75x can be used to determine the cost c, in dollars, of an item, where x is the department store price, in dollars. if the item has not sold in one month, the discount store takes an additional 20% off the discounted price and an additional $5 off the total purchase. the function d(y) = 0.80y - 5 can be used to find d, the cost, in dollars, of an item that has not been sold for a month, where y is the discount store price, in dollars. create a function d(c(x)) that represents the final price of an item when a costumer buys an item that has been in the discount store for a month. d(c(x)) =