Alexndra earns $125 from her paper route each month but she spends about $20 each month on personal expenses. to pay for a school trip that cost $800, about how much months does she need to save money? explain

It would take Alexandria 8 months to earn the money. 

125-20= 105 monthly earnings after personal expenses 
800/105= 7.6 which rounds to 8.

8x105= 840

Since she spends $20 of the $125 she makes a month, she really ends up with $105 a month.

Write an equation using 'm' to represents months. It will be the money earned a month times the number of months, and this will equal how much she needs ($800)

105m=800

To find how many months, divide each side by 105

m equals about 7.62

Since you aren't going to have just .62 of a month, you need to round. Since it is above .5, you round up to 8 months.