SOLUTION: 3u+z=15 U+2z=10

Algebra ->  Coordinate Systems and Linear Equations  -> Lessons -> SOLUTION: 3u+z=15 U+2z=10      Log On


   

Question 1018567: 3u+z=15
U+2z=10
Found 2 solutions by FrankM, ikleyn:
Answer by FrankM(1040) About Me  (Show Source):
You can put this solution on YOUR website!
3u+z=15
U+2z=10
double 1st equation
6u+2z=30
U+2z=10
subtract
5u=20
u=4
z=3

Answer by ikleyn(52786) About Me  (Show Source):
You can put this solution on YOUR website!
.
3u+z=15
U+2z=10
---------------- 

3u +  z = 15,    (1)
 u + 2z = 10.    (2)

Substitute u = 10 - 2z from (2) into (1). You will get a single equation for u:

3*(10-2z) + 2z = 10.

Simplify and solve it:

30 - 6z + 2z = 10,

30 - 10 = 4z, 

4z = 20, 

z = 20%2F4 = 5.

Now find u from (2).