Alexandra earns $125 from her paper route each month, but she spends about $20 each month on pesonal expenses . to pay for a school field trip that costs $800, about how many months does she need to save money

She needs about 7.6 months to pay for the field trip (could be rounded up to 8 months) To solve for this first find out how much she earns each month:
125-20= 105
Then divide 800 by 105 to find how many months she needs
800/105=7.619

4should be the last one n=4