(1+1/7+1/91/11）*1/7+1/9+1/11+1/21）-（1+1/7+1/9+1/11+1/21）*（1/7+1/9+1/11） (1 + 1 / 7 + 1 / 9 + 1 / 11) * (1 / 7 + 1 / 9 + 1 / 11 + 1 / 21) - (1 + 1 / 7 + 1 / 9 + 1 / 11 + 1 / 21) * (1 / 7 + 1 / 9 + 1 / 11) please calculate! Write the whole process!

(1+1/7+1/91/11）*1/7+1/9+1/11+1/21）-（1+1/7+1/9+1/11+1/21）*（1/7+1/9+1/11） (1 + 1 / 7 + 1 / 9 + 1 / 11) * (1 / 7 + 1 / 9 + 1 / 11 + 1 / 21) - (1 + 1 / 7 + 1 / 9 + 1 / 11 + 1 / 21) * (1 / 7 + 1 / 9 + 1 / 11) please calculate! Write the whole process!

Suppose 1 / 7 + 1 / 9 + 1 / 11 = a; 1 / 7 + 1 / 9 + 1 / 11 + 1 / 21 = B;
The original formula = (1 + a) * B - (1 + b) * a
=b+ab-a-ab
=b-a
=1/21

Calculation: (1) 4 + 7 + 10 + 13 + +298+301+298+… +13+10+7+4 （2）1+11+21+31+… +101+111+101+… +31+21+11+1
There should be a process and a simple formula

（1）（301-4）/3+1=100
4+7+10+13+… +298+301+298+… +13+10+7+4
=（4+301）*100-301
=30199
（2）（111-1）/10+1=12
1+11+21+31+… +101+111+101+… +31+21+11+1
=（1+111）*12-111
=1233