Isn't 2,351 the standardized form already?
there is word form: two thousand, three hundred fifty one
there is expanded form: (2* 1000)+ (3*100)+ (5* 10)+ (1* 1)= 2,351
For #7 - part a: greatest common factor (GCF) is 5.
Part b: cross out everything BUT 10 & 20.
