Question

If a+b=5 and 3a+2b=20,then the value of a+b is

Answer 1

a+b=5 _______(1)
3a+2b=20 _______(2)
from eq. (1)
b=5-a _______(3)
putting eq. (3) in eq. (2)
3a+2(5-a)=20
3a-2a+10=20
a+10=20
a=20-10
a=10 _______(4)
putting eq. (4) in eq. (1)
10+b=5
b=5-10
b=-5
hence, a=10, b=-5

I HOPE THIS WILL HELP YOU..

Answer 2

a+b=5
Multiply 2 on both sides,
2(a+b)=2×5
2a+2b=10---------(1)
3a+2b=20--------(2)
(2)-(1)
3a+2b=20
2a+2b=10
(-)________
a=10
Put a=10 in a+b=5
10+b=5
b=5-10
b=-5
Therefore,a=10 and b=-5

Hope it helps