Dakota runs a half-marathon every 6 weeks, and madison runs a half-marathon every 15 weeks. if they start now, in how many weeks will they again be running a half marathon at the same time?

Dakota runs every 6 weeks ... so he runs at 6 weeks, 12 weeks, 18 weeks, 24 weeks, 30 weeks

Madison runs every 15 weeks ... so she runs at 15 weeks, 30 weeks, 45 weeks

so they will both be running a half-marathon at 30 weeks <==