Well, you first want to distrubute that -4 over and that -3 over... Then just combine like terms, so here it is semi-step-by-step:
1. -4(3x-5)-3(2+7x)+15-10x
2. -12x +20 - 6 - 21x + 15 - 10x
3. -43x + 29
Your answer would be -43x + 29 after combining like terms! Hope I could help!
-Nick