Can someone me on number 5 and explain ?

Hello!

First you have to find angle BDA

The angles in a triangle add to 180

Subtract the know angles to get the missing one

180 - 60 - 75 = 45

Angle BDA = 45

Next you find what angle ACD measures

The angles in a triangle add to 180

Subtract the know angles to get the missing angle

25 + 45 = 70

180 - 70 - 60 = 50

Angle ACD is 50

Now you can find angle CBD

The angles in a triangle add up to 180

Subtract the know angles to get the unknown one

180 - 25 - 50 = 105

Angle CBD is 105

Since Triangle DBC has one obtuse angle it is an obtuse triangle

The answer is A) obtuse triangle

Hope this helps!

A) for the n row: 22+(n-1)×6therefore,b) 100-22=78that means (n-1)×6=7878÷6=1313+1=1414th row has 100 seats