Amber got 2 wrong out of 5 questions what would her grade in percentage be?

It depends on how much the questions were worth

The difference between -2 and 10 is 12, so the temperature needs to rise 12 degrees. What we have to do is divide 12 by 1 1/2 and that is 8. The temperature will have to rise by 1 1/2 degrees 8 times before it is 10 degrees. 
It does this every half hour, so 8 divided by 2 is 4 hours before it is 10 degrees.

It will be 8 A.M. when it is 10 degrees because 4 AM plus 4 more hours is 8. 
Hope this helps!