Question

How do you solve 3u + z = 15 and u + 2z = 10?

Answer 1

Answer:

Using Subsituition Method,

Let 3u + z = 15 be our 1st eqn. and u + 2z = 10 be our 2nd eqn.

in 1st eqn,

⇒3u +z = 15

z=15-3u,

Now put the value of z in eq 2,

⇒ u + 2z = 10

→u + 2(15-3u) = 10

→u + 30 -6u = 10

→-5u=10-30

→-5u= -20

→u = -20/-5

→u = 4

.

Now put the value of u in eq 1,

⇒3u +z = 15

→3(4) +z = 15

→12 +z =15

→z = 15-12

→z= 3

Answer 2

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

u + 2z = 10..........(2)

on multiplying 3 in equation (2),

3u + 6z = 30 ........(3)

equation (1) - equation (3)

-5z = - 15

z = 3

putting the value of z in equation (3),

3u + 6×3 = 30,

3u = 30-18

u = 12/3 = 4

u = 4 , z = 3