The sum of two numbers is 20. Twice one number is four more than four times the other. Write a system of linear equations and determine both numbers.

The weight v of an object on venus varies directly with its weight e on earth. a person weighing 120 lb on earth would weigh 106 lb on venus. how much would a person weighing 150 lb on earth weigh on venus?

Twelve less than a number is at most 20

An airplane travels at an unknown elevation before it descends 3 miles to an elevation of 15 miles. find the elevation of the plane before its descen.