Question

afla c si f stiind ca 14c+10f=618 si dedesubt 7c+24f=632 tragem linie si scrie 5c+5f=?

Answer 1

14c+10f=618
 7c+ 24f=632 |×2
5c+5f=?

14c+48f=1264 -
14c+10f=618
--------------------
 /    38f=  646;   f=17

14c+10×17=618
14c=618 - 170
14c= 448;  c=32

5×32+5×17=5×(32+17)=5×49=245

Answer 2

   14c+10f=618
   2(7c+5f)=618
       7c+5f=618:2
       7c+5f=309
Dar 7c+24f=632
Daca scadem ultimele doua relatii obtinem:
7c+24f-(7c+5f)=632-309
7c+24f-7c-5f=323
19f=323
f=323:19
f=17
Inlocuim in relatia 7c+5f=309 pe f cu 17
7c+5·17=309
7c+85=309
7c=309-85
7c=224
c=224:7
c=32

5c+5f=5(c+f)=5(32+17)=5·49 = 245