so have put this code line in hopping to gain the sum
df <- mutate(df, MAS_UK = (MAS_UK_1+MAS_UK_2+MAS_UK_3+MAS_UK_4+MAS_UK_5+MAS_UK_6+MAS_UK_7+MAS_UK_8+MAS_UK_9+MAS_UK_10+MAS_UK_11+MAS_UK_12+MAS_UK_13+MAS_UK_14+MAS_UK_15+MAS_UK_16+MAS_UK_17+MAS_UK_18+MAS_UK_19+MAS_UK_20+MAS_UK_21+MAS_UK_22+MAS_UK_23)/23)
is this corrects?