See tha attached pdf file and let me know how useful this answer is.
6x+4/5=8
subtract 6x from both sides
4/5=8-6x
multiply both sides by 5 to get rid of the fraction
4=40-30x
divide both sides by 2
2=20-15x
add 15x to both sides
15x+2=20
subtract 2 from both sides
15x=18
divide both sides by 15
x=1.2
First week : -1.9 + 3.5 = 1.6
2nd week : -2.4
original water level had an increase of 1.6 inches
new water level has a decrease of -2.4 inches
