According to Wollstonecraft, in what way will bettering women’s education benefit men?

Mary Wollstonecraft is often referred to as one of the forebearers of modern feminist theory. Her eighteenth-century work "A Vindication of the Rights of Woman" essentially postulated that the central issue of gender equality was a woman's right to an education. It's essential to note that this treatise was written at a time when patriarchal society largely viewed women as inferior to men in matters of reason, logic, and intellect.
Wollstonecraft felt these notions were ill-conceived because better educated women (like herself) would be in a more superior position to help contribute to society as a whole. Their contributions, therefore, would ultimately benefit men as well as other women who inhabited that society. Disallowing female contributions from the national discourse literally meant eliminating half of society's potential brainpower.
Moreover, she saw women as the primary educators of the young. Through education, women shaped the mindset of future generations for the benefit of mankind—men and women alike. More specifically, they were molding the minds of young boys who would grow into men and become tomorrow's leaders. Therefore, it was important as educators to be educated themselves.
In addition, she saw educated women as critical to a stable marital relationship, which would of course be of benefit to the man because it would lead to a more cohesive family unit and better sexual experiences. In other words, educated wife, happy life. She felt a woman with strong reasoning abilities and a deep well of knowledge could better maintain a marriage with a man who saw her as an equal, which, again, would result in better-educated children.

Wollstonecraft's ideas were considered radical in her time, but to us they can seem tame and even conservative. In her Vindication of the Rights of Women, she advocates for better education for women primarily so that women can become more useful and companionable wives to their husbands and better mothers to their children. 
She argues that instead of teaching women to be manipulative and silly by giving them little access to knowledge and ideas, women should be educated, like men, as "rational" people so that their husbands will want to talk to them and spend time to them, so that they can offer their husbands wise advice and manage the household well, and so that overall they contribute to the betterment of society. Women are as capable of reason as men, she argues, if they are given access to the same education. 
Wollstonecraft envisions separate spheres for men and women, with men out in public and women in the home. Because women are the parent that raises the children, she believes they should be educated to provide wise guidance. This would provide society with both better adult men and better wives for these men in the future.