Questions & Answers about Этот пакет весит пятьсот граммов.
Because пакет is a masculine singular noun. In Russian, words like this must agree with the noun in gender, number, and case.
So:
- этот пакет = this package / this bag (masculine)
- эта сумка = this bag (feminine)
- это окно = this window (neuter)
- эти пакеты = these packages (plural)
Here, пакет is masculine, so этот is the correct form.
Весит is the 3rd person singular present tense form of весить, meaning to weigh.
So:
- я вешу = I weigh
- ты весишь = you weigh
- он / она / оно весит = he / she / it weighs
- они весят = they weigh
In this sentence, the subject is этот пакет (this package), which is singular, so Russian uses весит: this package weighs.