Question

how to solve 3u + z=15
u+2z=10 by substitution method. plzz its urgent.

Answer 1

3u+z=15-----(1)

u+2z=10
=> u=10-2z----(2)

(1)=> 3u+z=15
=>3(10-2z)+z=15
=>30-6z+z=15
=>-5z= 15-30
=>-5z= -15
=>z=3

(2)=> u=10-2(3)
=> u= 10-6
=>u=4

Answer 2

3u+z=15 (1)
u+2z=10 (2)
From 1
z=15-3u (3)
(substitute 3 in 2)
u+2(15-3u)=10
u+30-6u=10
30-5u=10
30-10=5u
20=5u
20/5=u
4=u
Now, u =4 put this value in equation (3)
z=15-3(4)
z=15-12
z=3
Therefore,
u=4 and z=3