3 men does same work as 4 women in 43 days.

multiply 3 and 4 and 43 for a supposed amount of total work (516).

Now calculate how much work is done by 3 men in one day by dividing 516 by 43 (12). Then calculate one man work in one day by dividing 12 by 3 (4).

Same (12) amount of work is done by 4 women in one day. so one women does 12/4 (3) in one day.

now see there are 7 men and 5 women in the final team.
total amount of work in one day will be

7(4)+5(3) = 43

Now divide total work (516) by total work in one day (43) to get the answer (12)