Posted by sami sun on .
It takes matt 9 hrs longer to build a wall than it takes chris. Working together they can build the wall in 20hrs. how long would it take each working alone to build the wall?

Algebra 
mike,
Chris is x Matt is x+9
2x+9=20
2x=11
x=5.5
Chris = 5.5
Matt= 5.5+9 = 14.5
5.5 +14.5 = 20