3(2x + 4y -15z) (pls help qwq)

Ineed i been stuck on this question since yesterday

Lizette is training for a marathon. at 7: 00 she left her house and ran until 8: 30, then she walked until 11: 30. she covered a total distance of 18 miles. her running speed was six miles per hour faster than her walking speed. find her running and walking speeds in miles per hour.

What value is a discontinuity of x squared plus 8 x plus 4, all over x squared minus x minus 6?