As someone else has mentioned, 50 grams equates to 10 teaspoons. There are lots of different ways to work out the answer to this sort of question, but my usual method (when I'm cooking) is to use one of two pieces of equipment, neither of which I'd want to be without!
How to tell how many teaspoons of an ingredient to use, when measured in grams
For small quantities of cooking ingredients, I usually rely on one or other of my trusty sets of measuring spoons, which are like some of the ones shown in the picture below.
I have quite a collection of new and vintage ones, (which I mostly picked up at car boot or garage sales), some of which are really cute. They're also brilliant for measuring 1/4 or 1/2 teaspoonfuls, too.
The only trouble with the vintage spoons is that they were made before grams came into use - so I have to use a more modern version when trying to follow a recent recipe!
Other ways to measure small quantities of ingredients
I also rely quite heavily on traditional-style measuring cups, like the two below.
When it's vital to get the quantity right - measuring the quantity of a medicine
The best thing for measuring medicines is (obviously) a medicine spoon like the one below.
Pharmacists in the UK always used to issue these free, along with bottles of medicine, but don't always seem to these days. (Perhaps they've worked out they can charge extra for them now!)
Alternatively, perhaps they've realised that they can sell us more and more complicated versions of the same thing, like this one:
How to work out how many grams to how many teaspoons, if you don't posses any form of accurate measuring device?
The answer to this question's really simple: Use your computer, or smartphone to find the answer!
For example, if you tend to keep your laptop nearby while you cook, and need to know how to measure out a certain number of grams of an ingredient - then why not use one of the many online converters, like this one?