X : 20 = 40 * 3
x : 20 = 120
x = 120 * 20
x = 2400
---------------------
x * 110 = 110
x = 110 : 110
x =1
----------------------
x - 260 = 0
x = 260
3,4*(-1,8)=-6,12. -15/16*(-48/55)=3/2*6/11=18/22=9/11
7/9+1/9+3/8+5/8+4/7+3/7=(7+1)/9+(3+5)/8+(4+3)/7=8/9+1+1=26/9