Question 1179647
3 similar chocolate bars and 4 similar packets of candy weigh 200 g. 3 such 
chocolate bars and 7 such packets of candy weigh 260 g. What is the weight of a 
chocolate bar?
<pre>Let weight of a chocolate bar, and a packet of candy, be B, and C, respectively
Then we get: 3B + 4C = 200 ------ eq (i)
Also, 3B + 7C = 260 ------ eq (ii)
3C = 60 ------ Subtracting eq (i) from eq (ii)
Weight of a chocolate bar, or {{{matrix(1,6, C, "=", 60/3, "=", 20, g))}}}
Substitute 20 for C in either eq (i) or eq (ii) and solve for B to get the weight of a chocolate bar.

If you love to TORMENT yourself, then you can do the problem the way the other person did. 
I have no idea why she continues to make MOUNTAINS out of MIOLEHILLS with these simple-enough math problems.