Question 133194
How much salt is in the original solution?
{{{400 * 0.14}}} = 56

The amount of salt doesn;t change. So we need to find the ratio where 56 is 40% of some other number.

{{{56/n = 0.4}}}
{{{56/0.4 = n}}}
n = 140

In order to increase the salinity from 14% to 40%, you need to remove {{{400 - 140}}} = 260 gallons of water