5x-0.2x=19.2
12-4x=2.4
12:0.5=x:
3.14×16=
3.8+6.2 =
0.65 ÷ 1.3 =
×33=
-=
1 ÷ =
75×10%=
+×2=
3.06-[1.8×(2.41-1.91)]
6.12+3.78=
16×30%=
1.2+0.2×0.3=
0.25×2021×4=
4:x=0.2:25%
①x:15=4:5 ② ③ ④