3*21*7*28=(28*3)*(21*7) решить тагже 21*4*2*21,9*148*2,3*333*3*3*3

3*21*7*28=(28*3)*(21*7)                        28*3=30                               
3*21*7*28=30*147                                21*7=147
3*21*7*28=441                                     147*30=441    63*7*28=441                                        3*21=63  
441*28=441                                          63*7=441
12348=441
12348 больше 441