A+B+C= 1, in which A accounts for 40%, B and C account for 60%. Suppose A accounts for 40% and B+C accounts for 60%.

B and C decreased by 20% year-on-year, which was 80% of the same period last year.

Let a be x more than last year, and get.

40%*X+80%*60%= 1

Found X= 130%

So a will increase by 30% compared with last year.