Answer:
31 months.
Explanation:
1. Create the inequation.
Let "x" be the time (in months). Hence, the equation should look like this:
.
2. Substract 1250 from both sides of the equation.

3. Multiply both sides of the inequation by -1 and inverse the comparison symbol.

4. Divide both sides by 35.

5. Conclude.
The result of the inequation is 31.43. Since we are talking about time (in months), it would be more appropiate to say that Glenn can pay his phone for 31 months, because the balance on his account won't be enough to cover the 32th month without being charges with fees from the bank.