There are no duplicated observations in your dataframe (i.e. x and y values duplicated between rows) but this is an example of how to find duplicated x values in your sample dataframe.
library(tidyverse)
my_tib <- tibble(x = sample(100, rep = TRUE), y = sample(100, rep = TRUE))
my_tib %>%
group_by(x) %>%
filter(n() > 1) %>%
distinct(x, .keep_all = TRUE)
#> # A tibble: 22 x 2
#> # Groups: x [22]
#> x y
#> <int> <int>
#> 1 43 97
#> 2 80 98
#> 3 77 70
#> 4 12 100
#> 5 57 33
#> 6 72 72
#> 7 47 76
#> 8 100 88
#> 9 17 100
#> 10 26 34
#> # … with 12 more rows
If this doesn't solve your problem, please elaborate more in your question and reproducible example, you are not making very clear your request.