Question

faceti calculele din imagine​

Answer 1

a)

a+b = 20

b+c = 30

3a+7b+4c = 3a+(3b+4b)+4c =

= 3a+3b + 4b+4c =

= 3(a+b) + 4(b+c) =

= 3•20 + 4•30 =

= 60+120 =

= 180

b)

a+b = 33

a+c = 11

5a+3b+2c = (2a+3a)+3b+2c =

= 2a+2c + 3a+3b =

= 2(a+c) + 3(a+b) =

= 2•11 + 3•33 =

= 22 + 99 =

= 121