Answer:
x + 9y - 9
Have a good day! Brainliest?
Answer:
The angle between any two faces of this pyramid is equal to 
Step-by-step explanation:
we know that
An equilateral triangle has three equal sides and three equal internal angles of measure 60 degrees
In this problem
All the faces in the regular triangular pyramid are equilateral triangles.
therefore
The angle between any two faces of this pyramid is equal to 
5 x 3 = 15
30 x 3 = 90
15+90=105
so that person paid $105 for that day