File list (Check if you may need any files):
Withinplusorminus20subtractionofnaturalnumbers\MSSCCPRJ.SCC
..............................................\工程1.vbw
..............................................\Form3.frm
..............................................\Form2.frm
..............................................\20以内加减.exe
..............................................\20以内截图.doc
..............................................\Form1.frm
..............................................\工程1.vbp
Withinplusorminus20subtractionofnaturalnumbers