I’m stuck on this, can someone explain ? !

first off, I'd like to point out that for the 5th test, he has 96, and that's +6 above 90, and therefore it should be 6.

if all the above/below numbers, summed up yield 0, that simply means the average is an even 90 on average for all 6 tests, if they yield above 0, is above on the average, and if it's below 0, a negative value, he needs to do more work.

-7+4-11+7+6-3 = -4.

you can think of it this way, if he had 90 on all 6 tests, the above/below row will show 0, 0, 0, 0, 0, 0. If any of the tests was above 90, that row will yield a sum more than 0, and if any of the tests were below, that sum will be a negative value.

m∠cdf = 43° , m∠gdf = 114°, m∠gde = 23°, m∠edh = 23° , m∠cdh = 157°

step-by-step explanation:

since, it is given that de bisects the angle gdh ⇒ de divides the angle gdh into two equal angles.

⇒ m∠gde = m∠edh

⇒ 8·x   - 1 = 6·x + 5

⇒ x = 3

so, m∠gde = 8·x - 1 = 23°

and m∠edh = 23°

now, it is given ∠cde is an straight angle so, m∠cde = 180°

⇒ m∠cdf + m∠fdg + m∠gde = 180°

⇒ 43° + m∠fdg + 23° = 180°

⇒ m∠fdg = 114°

again, m∠cde = m∠cdh + m∠edh = 180°

m∠cdh + 23° = 180°

⇒ m∠cdh = 157°