How do I do this (probably very easy) math problem

It's not homework, it's just a personal goal that I started 3 days ago. Everyday I will do push-ups, adding 5 each day. I started with 10, and then I did an extra 5 yesterday and an extra 5 so today I did 20 push-ups. If I add 5 push-ups every day for 4 months (let's just say every month is 30 days long). Thanks.

It would be a huge number, it is quite an unrealistic goal.
The last day of the 4 month period, you would be doing 610 pushups. You would be able to do this routine for a month or so, but when you start to reach 200 pushups, you probably wont be able to keep doing that many right after doing it the day before. ( I'm assuming you are doing these pushups in one setting ). If you plan on doing the total throughout the day, then i suppose it is a reasonable goal.

I would be able to calculate the sum if your series was geometric (using the formula for equating the sum of a geometric finite series a/(1-r) )....However the series s_(n-1) + 5 starting at 10 is not geometric. There probably is a way to do it though

pushups = 10 + 5*(days-1)

for example the 5th day

10 + 5 * (5-1)
=30

sub in 30 days x 4 months = 120
10 + 5 * (120-1)
=605

5•30+20=170 pushups

You have 20 now + 4 months(120 days) .. Now 120x5, 600+your current 20.. 620. phew, are yeww superman?

You do more than over 200