Hey there!
Set up an equation. This would be 4+0.5x=12. You have to get x by itself, so subtract 4 on each side. You get 0.5x=8. Divide by 0.5 on each side to get x=16. Heidi purchased 16 tickets.
I hope this helps!
The next palindromic number is 16061, so he traveled 110 miles. 110 miles/2 hours = 55 mph.
For both problems, we can use the section formula.
1) 
2) 
Do them backwards and you will get the answer
The relationship is negative 4