SOLUTION: Sally bought three chocolate bars and a pack of gum ad paid 1.75. Jake bought two chocolate bars and four packs of gum and paid 2.00. Find the cost of a chocolate bar and the cost

Sally bought three chocolate bars and a pack of gum ad paid 1.75. Jake bought
two chocolate bars and four packs of gum and paid 2.00. Find the cost of a 
chocolate bar and the cost of a pack of gum.

3C+G=1.75
2C+4G=2

-3c on the first equation
G=1.75-3C

Replace G in the second equation with its equivalent, 1.75-3C
2C+4(1.75-3C)=2   SIMPLIFY by DISTRIBUTION
2C+7.00-12C=2     -7.00 BOTH SIDES
-10C=-5           divide by -10, both sides
C=.50             A chocolate bar costs 50 cents, or $.50

Now plug C in to the second equation
2(.5)+4G=2        Simplify
1+4G=2            -1 both sides
4G=1              divide by 4
G=.25             A pack of gum costs 25 cents, or $.25

The answers:
A chocolate bar costs $0.50
A pack of gum costs   $0.25