Question

How many gallons of 30% antifreeze should be mixed with 10 gallons of 93% antifreeze to obtain a 65% antifreeze mixture ?

Answer 1

The answer to this question is 9.9

Answer 2

0.3*x+0.75*10=0.55(10+x)
0.3*x+7.5=5.5+0.55x
0.3x-0.55x=5.5-7.5
-0.25x=-2
x=8 liters at 30% is added to 10 liters of 75% to get 18 liters at 55%

NOW! Let;s check if it's the right answer
0.3*8+0.75*10=0.55(10+8)
2.4+7.5=0.55(18)
9.9=9.9