楼主 (北美华人网)
$32包邮 (Media mail) https://www.amazon.com/Workbook-State-Standards-Subtraction-Homeschool-Classroom/dp/1483835480/ref=sr_1_3?crid=3R36CUXEQHYOV&keywords=spectrum+critical+thinking+for+math+grade+1&qid=1642095011&s=books&sprefix=spectrum+critical+thin%2Cstripbooks%2C122&sr=1-3 https://www.amazon.com/Singapore-Workbook-2nd-Addition-Subtraction-Multiplication/dp/1483813185/ref=sr_1_2_sspa?crid=35JTGOWE6USO&keywords=singapore+math&qid=1642095048&s=books&sprefix=singapore+math%2Cstripbooks%2C132&sr=1-2-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFERUJOVzFTODVBOEwmZW5jcnlwdGVkSWQ9QTAzODcxODJEU001QUZTVElZUlomZW5jcnlwdGVkQWRJZD1BMDM3NzAxNzJDMzIzNTlBN1FINVcmd2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl https://www.amazon.com/Singapore-Challenging-Problems-Complete-Books/dp/B078995M56/ref=sr_1_3?crid=1VRGR95TYT1J2&keywords=singapore+math+challenge+word+problems+1&qid=1642095092&s=books&sprefix=singapore+math+challenge+work+problems+1%2Cstripbooks%2C114&sr=1-3 
