A right angle is 90 degrees, an obtuse angle is larger than 90 degrees and an acute angle is less than 90 Degrees.
The angle shown is smaller than 90 degrees so it is c. Acute
Yes 28/30 is bigger than 4/5.
.5 is basically 1/2. We know this because .5 written as a fraction is 50/100 which you can simplify to 1/2.
6/10 is greater than 1/2. You can find this out by converting 1/2 to tenths. Multiply the numerator and the denominator by 5 to get 5/10. From there you can easily see that 6/10 > 5/10.
As for the number line simply use 10ths: 1/10, 2/10, 3/10 ... and input 6/10 and 5/10 in the appropriate areas.