bob needs to save at least 10 dollars to buy that book
he gets 2 dollars in allowance every day
he has 3 dollars now
in how many days will he be able to buy the book?
translation
if d=number of days
then
how much has now+how much will earn≥10
3+2d≥10
solve
minus 3 both sides
2d≥7
divide both sides by 2
d≥3.5
but wait, you can't have 3.5 days, round up becuase if round down you wil have less than $10
answer is 4 days
that is an example, just read it and don't just report it
