Question

Daca 2-b=a si b+c=7 , atunci 3a+5b+2c=

Answer 1

putem face in mai multe moduri . cel mai usor:
2-b=a
adica 2=a+b
b+c=7
scriem
3a+5b+2c=3a+3b+2b+2c=3(a+b)+2(b+c)=3•2+2•7=6+14=20