3/4-1,75; 2/3+0,75; 3/7-0,8; 0,04+9/16 !

1) 3/4 -1,75 =3/4 -175/100 =3/4 - 1 3/4 = -1.
2)  2/3 + 0,75 = 2/3 +75/100 =2/3 +3/4 =(4*2+3*3)/12 = 17/12 = 1 5/12.
3)  3/7 -0,8 = 3/7 - 8/10 = (3*10 - 7*8)/70 =(30-56)/70 = -26/70 = -13/35.
4) 0,04+9/16 = 4/100+9/16 =(4*4+ 25*9)/400= (16+225)/400= 241/400. 

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