Question

daca a,b si c sunt trei numere naturale astfel in cat a+b=23 si b+c=31, atunci determina valoarea expresiei 5×a+7×b+2×c

Answer 1

a + b = 32   si b + c = 31

5 × a + 7 × b + 2 × c = 177

= 5 × a + ( 5 × b + 2 × b ) + 2 × c =

= 5 × ( a + b ) + 2 × ( b + c ) =

= 5 × 23 + 2 × 31 =

= 115 + 62 =

= 177