1) (3/4 + 1/5)*(5/19)=(15/20+4/20)*5/19=(19/20)*(5/19)=5/20=1/4=0,25
2) (12цел 1/3 - 7цел 3/4) * 6/11=(12цел 4/12-7цел 9/12)*6/11=(148/12-93/12)*6/11=55/12*6/11=5/2=2,5
3)(2цел 3/5 - 5/8):19цел 3/4=(2цел 24/40 - 25/40):19цел 3/4=(104/40-25/40):19цел 3/4=79/40:79/4=79/40*4/79=1/10=0,1