Can someone explain to me how to solve this? use elimination to solve each system of equations. x + y = 7 x - y = -3

After t seconds, a ball tossed in the air from the ground level reaches a height of h feet given by the equation h = 144t-16t^2. after how many seconds will the ball hit the ground before rebounding?

In the field of thermodynamics, rankine is the unit used to measure temperature. one can convert temperature from celsius into rankine using the formula , what is the temperature in celsius corresponding to r degrees rankine? a. 9/5(c - 273) b. 9/5(c + 273) c. 5/9( c - 273) d. 5/9( c + 273)

Kerion has a beaded necklace business. she can make 12 necklaces is 2 hours. how long will it take her to make 9 necklaces?