SOLUTION: find two numbers with a sum of 15 and a differnce of 4.

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: find two numbers with a sum of 15 and a differnce of 4.      Log On


   

Question 98949: find two numbers with a sum of 15 and a differnce of 4.
Answer by tutorcecilia(2152) About Me  (Show Source):
You can put this solution on YOUR website!
x+y=15
x-y=4
.
Solving using the substitute method:
x+y=15
x=-y+15
.
Substitute (x=-y+15) back into the second equation and solve for the y-term
x-y=4
(-y+15)-y=4
-2y+15=4
-2y=-15+4
-2y=-11
y=11/2
.
Solve for the x-term by substituting (y=11/2) back into either equation and solve for the x-term:
x-y=4
x-(11/2)=4
x=4+11/2
x=19/2
.
Checking:
x-y=4
(19/2)-(11/2)=4
8/2=4
4=4 [checks out]