i believe the equqation will be 9400 - 800m > 3000
subtract 9400 from both sides of this equation to get -800m > 3000 - 9400
simplify to get -800m > -6400
divide both sides of the equation by -800 to get m < 8.
when you multiply or divide both sides of an inequality by a negative number, the inequality reverses.
you had -800m > -6400 and you divided by -800 which reversed the inequality and got you m < 8.
the balance in the account will be > 3000 when m is < 8.
you can confirm using the original equation.
the original equation is 9400 - 800m > 3000
when m = 8, you get 9400 - 800*8 > 3000 which results in 9400 - 6400 > 3000 which results in 3000 > 3000 which is NOT true because 3000 is equal to 3000.
so m can't be 8, which is ok because the solution says that m had to be less than 8.
you can also look at the remaining balance at the end of each month as shown below:
month balance
0 9400
1 8600
2 7800
3 7000
4 6200
5 5400
6 4600
7 3800
8 3000 *****
month 7 is the last month when the remaining balance is > 3000.