This is an extremely common question and one with an extremely open answer.
Nobody can be asked this question and answer it without knowing a bit more about the person who is asking.
There are so many factors to exercise which can cause people additional stress in their lives if they feel that they are not doing enough.
So what are the things we need to consider when answering this question...
1. What type of exercise do they enjoy?
I mean what is working out if you do not enjoy it? There are so many different ways of exercising it is important to understand that not every single person has the same enjoyment levels as you do.
Finding out if they enjoy weightlifting, high intensity, strength training, running swimming or maybe something more "relaxed" such as general classes or yoga.
2. How much time do they have to train?
A common mistake when giving someone a plan is expecting them to be able to pluck some free time out of the air.
We all have our own busy lives and schedules that we have to deal with and maybe spending 2-3 hours preparing, driving to and from the gym along with working out 3 times a week just isn't do-able.
My suggestion would be to sit down with a diary along with your partners and work out which days you do have time to allow for YOU. This may mean not sitting down and watching the latest series of Ru Pauls drag race and spending this time instead looking after No 1.
Do not over commit.
If you feel that you can fit in 3 times a week, then allow for 2 and if you do manage to get that 3rd in then that is a lovely added bonus.
3. What is your experience?
If you are inexperienced in your workout choice then you may not get the most efficient workout right away.
Do your research and maybe even INVEST into a Personal Trainer. Many PT's will offer a free induction session to get to to know them and check to see if there is a fit between the 2 of you.
Can they really help you on your journey or are they more driven to a type of workout that doesn't suit you.
Running into any sort of exercise without the correct knowledge can be detrimental to your progress and health.
There is no right or wrong answer to this question, as such.
Take time to sit down and make a plan.
Do not over commit to do many days
Invest in a coach / personal trainer if required
If possible find a friend who has a similar want to change their ways.