If 7 men and 4 women working together can do five times as much work per hour as one man and one woman together, then the ratio of the work done by a man and that of a woman for a given time is:

Let the efficiency (work done per hour) of a man be M and that of a woman be W.
According to the question:

7M+4W=5(1M+1W)
7M+4W=5M+5W
7M−5M=5W−4W
2M=1W
W
M
​
=
2
1
​

Thus, the ratio of work done by a man and a woman for a given time is 1:2.