с действиями 1 3/4-7/8(4/9+1/18)=

1 3/4 - 7/8 (4/9+1/18)=1  5/16
 1) 4/9+1/18 =8/18+1/18=9/18=1/2
2) 7/8*1/2=7/16
3) 1 3/4 - 7/16 =7/4-7/6 = 28/16 -7/16=21/16 =1  5/16