3, \frac{9}{2},\frac{27}{4},... 3,
2
9

,
4
27

,...
\text{Find the 10th term.}
Find the 10th term.

We first model the equation that expresses the problem. We let x be the amount of water evaporated.
0.05(70) = (0.075)(70-x)
Take note that we modeled this expression by keeping in mind that the amount of solute (salt) will always be equal, and it is the solvent (water) that will change therefore affecting the percentage of the concentration of the solution.

Solving for x:
70 - x = 0.05(70)/(0.075)
x = 23.3 lbs of water.