My sister is young.She can't look after herself.合并成一句

My sister is young.She can't look after herself.合并成一句
1.My sister is young.She can't look after herself.合并成一句
My sisiter is ____ ____ ____ to look after herself.
2.He bagan to learn the piano when he was 7.改为同义句
He bagan to learn the piano ____ ____ ____ ____ seven.
第一题有3个空啊。别回答2个单词。