4-(4цел.21/40-5,25):1цел.9/20

4 - (4 21/40 - 5 1/4 ) : 1 9/20 = 4,5
1) 181/40 - 21/ 4 =(181-210) /40 = - 29/40
2) -29/40 : 29/20 = -1/2 = -0,5
3) 4 + 0,5 = 4,5