The three scores are 86, 74, and an unknown score x. The average (i.e. the sum divided by how many there are) is 80, so we have
Multiply both sides by 3 and you get
Subtract 160 from both sides to get
Note: you could solve this exercise very quickly if you notice that the two numbers, 86 and 74, are symmetrical with respect to 80, which is the average. So, the third number must be the average.
In the parallelogram, m∠M is equal to m∠O, and the sum of m∠M and
m∠N is 180°.
Response:
The true statements are;
The possible drawing of the parallelogram LMNO created with MS Visio is attached.
From the drawing, we have;
m∠M = 11·x
m∠N = 6·x - 7
The properties of a parallelogram are;
Opposite angles are equal.
Adjacent angles are supplementary
Which gives;
11·x + 6·x - 7 = 180°
17·x = (180 + 7)° = 187°
m∠M = 11 × 11° = 121° = m∠O
m∠N = 6 × 11° - 7 = 59° = m∠L
Therefore;
The statements that are true are;
Learn more about the properties of a parallelogram here:
