(1)8:5=X:15,
5x=8×15,
5x=120,
5x÷5=120÷5,
x=24;
(2)8X+3×0.9=6.3,
8x+2.7-2.7=6.3-2.7,
8x=3.6,
8x÷8=3.6÷8,
x=0.45;
(3)
:3 4
=20:X,1 5
x=3 4
×20,1 5
x÷3 4
=4÷3 4
,3 4
x=5
;1 3
(4)
=0.8:25,x 10
25x=10×0.8,
25x÷25=8÷25,
x=0.32;
(5)
x+1 3
x=5 6
,1 6
x=7 6
,1 6
x÷7 6
=7 6
÷1 6
,7 6
x=
;1 7
(6)1:X=0.4:8,
0.4x=1×8,
0.4x÷0.4=8÷0.4,
x=20.