有一对父子，他们年龄相差20岁零六个月．父亲的岁数又是儿子岁数的3倍。请问：再过多少年，父亲的岁数是儿子的2倍？
直接写数对又快：+=﹣= 2012×= 56÷11×165÷7=×[0.75+（﹣）]= 40÷[×（+）]=
口算． 80×20%= 24×0.2= 5﹣=÷3= 32= 36÷12%= 1﹣0.3= 2.1+3.25=×1.8=（0.2）2×52=
直接写出得数． 2.8÷0.125= 4.38﹣3.42+5.62﹣2.08=== 9.08×9+9.08==
直接写出得数． ④36.36÷36= ②×= ③2.5×1.5×4=
直接写得数． 1÷0.05= 0.325+=（0.2）2= 10﹣0.01== 3.1×0.7=
+
=
﹣
= 2012×
=
×[0.75+（
﹣
）]= 40÷[
+
）]=
=
÷3= 32=
﹣0.3= 2.1+3.25=
×1.8=（0.2）2×52=
=
= 9.08×9+9.08=
=
×
=
=（0.2）2=
= 3.1×0.7=
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