11x-13y=89
-11x+13y=107
solve with elimination

Harold wrote this equation to model the level of water in a pool over time. the variable x represents time in hours. f(x) = 3,500 - 225x which statements about the situation are true? check all that apply. the water level is rising. the water level is falling. the initial level of water in the pool was 3,500 units. the initial level of water in the pool was 225 units. the pool was empty after 14 hours. the water was 2,600 units high after 4 hours.

Aboat has a speed of 9 mph in calm water. it takes the boat 4 hours to travel upstream but only 2 hours to travel the same distance downstream. which equation can be used to find c, the speed of the current? 2(9 – c) = 4(9 + c) 9 + c = 4(9 – c) 9 – c = 2(9 + c) 4(9 – c) = 2(9 + c)

David and alton are training for a race. they spend 35 minutes stretching and then go on a 5 mile practice run. david runs at a pace of 7 min/mile. alton runs at a pace of 8 min/mile. write an equation for each runner that shows the total length of their workout. then solve each equation showing your work