Then 50 * x * 30 = 24 * x *10+20 * y * X.
1500X=240X+20YX
1260X=20XY
1260=20Y
Y=63
Second, A has X tons of coal and B has Y tons of coal.
X+Y=760
760-592= 1/4X+ 1/5Y
rule
X+Y=760
168 = 1/4X+ 1/5Y
Y=440
X=320
Thirdly, assuming that the total workload is 1, the workload of Party A and Party B working together 12 days is greater than the total.
The big amount is the amount that A didn't participate in, and then divided by A's daily workload is the number of days.
[( 1/ 15+ 1/20)* 12- 1]/( 1/ 15)=6
Method 2: Assuming that the daily workload of Party A is "1", the total workload is 1× 15= 15. Because Party B completes this total workload in 20 days, the daily workload of Party B is: 15/20=3/4 (quantity.
Because he worked 12 days, then B worked 12*3/4=9 of the total.
Then the remaining amount is obtained by A: 15-9=6.
A The daily workload is "1", so it takes 6/ 1=6 days.
A *** 12 days, A worked for six days, so she had a rest for six days.