Question

Daca: a-2b=17 si a+b+3c=53 calculati a+2c
stiind ca a+2b=60 si b+3d+2c=80 aflati valoarea sumei:
S=3a+11b+15d+10c+120

Answer 1

1.
 a-2b=17
 a+b+3c=53 |*2
 

a-2b=17    +
2a+2b+6x= 106
---------------------
3a+6c= 106+17

3*(a+2c)=123  | :3
a+2c= 41

2.
a+2b=60
b+3d+2c=80
                                  


3*(a+2b)+5*(b+3d+2c)= 3a+6b+5b+15d+10c= 3*60+5*80=180+400=580

  S=3a+11b+15d+10c+120 = 580+120= 700