It costs $3.92 to send all 14 postcards. Or is this a trick question.
The result of adding the answer together is 1
The answer to the question is 8
We have 60 gallons of 20% antifreeze.
How much 70% antifreeze do we add to get 60% antifreeze?
We'll make "x" the gallons of 70% we must add.
.20 * 60 + .70 x = .60 * (60 + x)
12 + .70x = 36 + .60x
.10x = 24
x = 240 gallons of 70% antifreeze.
Source
1728.com/mixture.htm (see example B)
