library(dplyr, warn.conflicts = FALSE)
library(rlang)

df <- tibble::tibble(a = 1, b = 2, c = 3)

cols <- set_names(c("a", "b"), c("x", "y"))

df %>%
  mutate(
    across(
      .cols = all_of(cols),
      .fns = ~ .x + 10
    )
  )
#> # A tibble: 1 × 5
#>       a     b     c     x     y
#>   <dbl> <dbl> <dbl> <dbl> <dbl>
#> 1     1     2     3    11    12