isosceles triangles are ones that have two equal sides and angles. this would mean that ab is equal to bc. then you substitute the values in for AB=BC, 3x-4=5x-10. you bring the variables to one side and you flip everything which is then 2x=6 and then divide by 2. this would be x=3. then you have to figure out the AB. 3(3)-4=5. then you can always check for BC, 5(3)-10=5. and they are equal! hope i helped!