Whenever you see a fraction where the denominator is exactly twice as big as the numerator, you know that it equals 0.5 or the other fractions that equal 0.5
For the first angle (a): This angle is slightly above 90 degrees. Since we're estimating values to the nearest 10 degrees, therefore, this angle is probably 100 degrees. It is an obtuse angle (since its measure is greater than 90)
For the second angle (b): This angle is approaching 180 degrees (it is approaching being a straight angle), however, it is still below 180 degrees, so it is probably around 170 degrees (to the nearest 10 degrees). It is also an obtuse angle.
For the third angle (c): Its measure is below 90 degrees by around 20 degrees (estimated value of course). By estimation, this angle is around 70 degrees (to the nearest 10 degrees). It is an acute angle (since its measure is less than 90)
