Can someone help me step through this to help me get the answer correct

In which source of water would a wave travel the fastest? o ice o cold o room temperature o hot mark this and return save and exit next

Suppose that the price p (in dollars) and the weekly sales x (in thousands of units) of a certain commodity satisfy the demand equation 4p cubedplusx squaredequals38 comma 400. determine the rate at which sales are changing at a time when xequals80, pequals20, and the price is falling at the rate of $.20 per week.

Find an equation for the linear function which has slope -10 and x-intercept -7