Hi, and welcome!

The key to getting more and better answer lies in the FAQ: What's a reproducible example (`reprex`) and how do I do one?

For your problem, at a minimum it should look like

```
dat <- c(1000,1000,200,200,200,200,100,100,100,100,100,100,60,60,60,60,60,60,45,45,45,45,45,45,45,45,12,24,12,24,12,24,12,24,12,24,12,24,12,24,12,24,12,24,12,24,12,24,12,24)
```

^{Created on 2020-02-13 by the reprex package (v0.3.0)}

and, ideally, what you have tried.

Also, if applicable, see FAQ: Homework Policy

So, to start you need the median.

```
med <- median(dat)
```

Next, you need to subset for all observations *below* the median (assuming that you don't be *at or below* the median).

```
lower <- dat[dat < med]
```

The sum is easy enough

```
tot <- sum(lower)
```

as is the number of observations

```
obs <- length * tot
```

And with that, the `+`

operator will give you a final result.