A tank holds x gallons of a saltwater solution that is 20% salt by volume. One Fourth of the water is evaporated, leaving all of the salt. When 5 Gallons of water and 10 gallons of salt are added, the resulting mixture is 33 1/3 % salt by volume. What is the value of x? Choose the most appropriate option:
A) 37.5
B) 75
C) 100
D) 150
E) 175
Nope, 150. I can only get it by following PR's backsolving explanation. I hate that.   Original mixture has 20% salt and 80% water.   Total = x   Out of which Salt = 0.2x and water = 0.8x   Now, 1/4 water evaporates and all salt remains.   So what remains is 0.2x salt and 0.6x water.   Now 10 gallons salt is added and 5 gallons of water is added.   So salt now becomes -&gt; (0.2x + 10) and water --&gt; (0.6x+5)   Amount of salt is 33.33% of total. So amount of water is 66.66%. So salt is half of the volume of water.   So (0.2x+10) = (0.6x+5)/2 = 0.4X+20 = 0.6X+5 =&gt;0.2X=15   Solving, x = 75   Answer : 75
<result>B</result>
A tank holds x gallons of a saltwater solution that is 20% salt by volume. One Fourth of the water is evaporated, leaving all of the salt. When 5 Gallons of water and 10 gallons of salt are added, the resulting mixture is 33 1/3 % salt by volume. What is the value of x?