The ratio between the number of men and women in an office is 5 : 7. If the number of women working in the office is 56. Find the number of men working in the office.

Given that the ratio between the number of men and womein in office is $5:7$

The number of women working in the office is $56$

it implies that $7x=56\Rightarrow x=8$

Therefore, the number of men in the office is $5x=5\left(8\right)=\boxed{\mathbf{40}}$