Filtering rows based on particular value in column

[sai_matcha]

Data i have

id  <- c(1,1,2,2,3,3,4,4,5,5)
amt <- c(250,NA,750,NA,750,NA,500,NA,750,NA)
dv  <- c(NA,1,NA,2,NA,1,NA,5,NA,4)
df  <- data.frame(id,amt,dv)

now i want to select ids who have amt of 750

output i need

id  <- c(2,2,3,3,5,5)
amt <- c(750,NA,750,NA,750,NA)
dv  <- c(NA,2,NA,1,NA,4)
df  <- data.frame(id,amt,dv)

please help me to do this .
thanks