50%x﹣0.2x=15;
=12; 6:30=x:0.5.
①x﹣
X=
②x:20=0.5:7.
①x+
x=27
②
= 
x=
=2∶3.5x=

X=

X=
x-5%x=17.5
=4:
x-
x=5
=4:3
x+
x=42
=3.2:x
x=
=
=
=58:87
:x=2.2:55
x-
x=0.375
-
x=
+
x=
:x=
=
:x
=
:
x=10