How would you eliminate or stop the "gang" problem?
Gangs are, in many ways, a product of poverty and inadequate socialization and education. Because many children from inner city homes lack the support infrastructure necessary for successful lives outside the structure of gangs, and do not perceive that they have chances for successful careers, they turn to gangs and crime as a combination of a social support structure and site of economic opportunity (primarily via dealing drugs).
Successful programs to reduce gang membership normally include a mixture of community policing and support programs to help young people develop after school activities and social networks, as well as the personalized tutoring that will enable them to continue on to university and find satisfying careers.
Reducing or eliminating the drug trade by a combination of limited legalization and increased policing would also be helpful.