Jika a+b=2 dan b+c=7,maka nilai a+b+c adalah....

a + b= 1
a+ c = 2
b+c= 7

a + b = 1
b = 1 - a

a + c = 2
c = 2 - a

b + c = 7
(1 - a) + ( 2 - a) = 7
3 - 2a = 7
- 2a = 7 - 3
- 2a = 4
a = -2

b = 1 - a = 1 - (-2)= 3
c = 2 - a = 2 - (-2) = 4

a + b+c = -2+3+4= 5

jawab b.5