Is this the kind of thing you're looking for? I've given a "base R" method and one using {dplyr}.
# BASE
df <- data.frame(
dur = seq(0, 500, 50),
age = seq(0, 1000, 100)
)
df[df$age - df$dur >= 216,]
#> dur age
#> 6 250 500
#> 7 300 600
#> 8 350 700
#> 9 400 800
#> 10 450 900
#> 11 500 1000
# TIDYVERSE
library(dplyr)
#>
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#>
#> filter, lag
#> The following objects are masked from 'package:base':
#>
#> intersect, setdiff, setequal, union
tibble(
dur = seq(0, 500, 50),
age = seq(0, 1000, 100)
) %>%
filter(age - dur >= 216)
#> # A tibble: 6 × 2
#> dur age
#> <dbl> <dbl>
#> 1 250 500
#> 2 300 600
#> 3 350 700
#> 4 400 800
#> 5 450 900
#> 6 500 1000
Created on 2022-07-30 by the reprex package (v2.0.1)