Uh oh! Wolfram|Alpha doesn't run without JavaScript.
Please enable JavaScript. If you don't know how, you can find instructions
here
.
Once you've done that, refresh this page to start using Wolfram|Alpha.
3 个数之和为30;第二个是第一个的两倍;第三个等于其他2个之和。求出。
3 个数之和为30;第二个是第一个的两倍;第三个等于其他2个之和。求出。
Natural Language
Math Input
Extended Keyboard