3((17/90)-0.125/(1 1/18))/480
3·((17/90)- 0.125/(1 1/18))/480 = 241/547200
1) 0.125/(1 1/18) = 1/8 : 19/18 = (1 · 18 )/ (8·19) = 9/76
2) 17/90 - 9/76 = 646/3420 - 405/3420 = 241/3420
3) 3·(241/3420) = 241/1140
4) (241/1140) : 480 = 241/547200