Continuous Error in score_homework() : argument "x" is missing, with no default

I am trying to build a function that takes a numeric vector of homework scores (of length n), and an optional logical argument drop, to compute a single homework value. If drop = TRUE, the lowest HW score must be dropped. The function should also return the average of the homework scores—but are I am not using mean().

step 1---- create a function to remove NA

 remove_missing <- function(x){a<-is.na(x)x[!a]}

step2 create a function to drop lowest score

 drop_lowest <- function(x,na.rm=TRUE) {if(na.rm==TRUE){
  x = remove_missing(x)}
    minX  <- x[1] ## set target to first element of `x`
    for (i in 1:length(x)) { ## i take values 2, 3, ..., length(x)
    if(x[i] < minX) ## do comparison with current target
    minX  <- x[i]  ## if element i is smaller than target, update 
    target
     }

    return(x[x != minX])
     }

step3 function to get average

    get_average <- function(x,na.rm=TRUE) { 
   if(na.rm==TRUE){
         x = remove_missing(x)}
       total <- 0
       for (n in 1:length(x)) {
total= total  + x[n]

    }
   return(total/length(x))
  } 

put it all together

    score_homework <- function(x,drop=TRUE)  
     {
     if(drop==TRUE)
       x = drop_lowest(x)
    {get_average(x)}}

However I keep getting the error Error in score_homework() : argument "x" is missing, with no default