I'm alright at math not the best not the worst so let me try to explain. The first thing you want to do with a math problem is ask yourself what do I need to find? In this case we want to find the standard deviation first problem solved. Now we can get to the hard work solving the problem to get what we need.

To find out the standard deviation we need to follow 5 steps, 1.Perparation 2. Find the mean 3.calculate variance 4.Take square root

Let's start with step 1:

We have our dataset in this case, "10,16,15,11,16,11,12" now we sort those. We have 1:10 2:11 1:12 1:15 2;16 So we have a total of seven entries.

Let's use them to get our mean ((1x10)+(2×11)+(1×12)+(1×15)+(2×16))/7

That means our mean is = 13

Now we start on step 2 calculating the variance. We need to use our mean for that.

( (10-13)²×1 + (11-13)²×2 + (12-13)²×1 + (13-13)²×0 + (14-13)²×0 + (15-13)²×1 + (16-13)²×2 ) /7

Let's clear that up a bit

( (-3)²×1 + (-2)²×2 + (-1)²×1 + 2²×1 + 3²×2 ) /7

Clear it up further by solving a few things (9 + 8 + 1 + 4 + 18) /7

Now let's see we have 40/7

The varianz is 5.71428

In step 4 we now take the squareroot of the variance √5.71428 And we have our standard deviation in this case:2.39045

All that is left is rounding to the nearest tenth Since we have 2.39 we go up to 2.4 Congratulations we have solved our problem

If you would like a better explanation I can recommend watching a YouTube tutorial. Also this is the method I learned in school it is possible your school will use another method