You can eliminate 81 because we know 
The dot is on approximately 9.32 (my estimate) so I would square that number:
(9.32)² = 86.8624 so if you round this you get 87
This is a triangular prism.
The lateral faces are triangles; this means that the two bases are parallel to one another. This makes it a prism instead of a pyramid.
The bases being triangles makes it a triangular prism.
Write an equation system based on the problem
"Agatha is five times older than her son, Bob" could be written as:
a = 5b.......(first equation)
"Three years ago, she was nine times older" could be written as:
a - 3 = 9(b - 3)......(second equation)
Solve the equation system
To find the value of b, substitute 5b as a to the second equation
a - 3 = 9(b - 3)
5b - 3 = 9(b - 3)
5b - 3 = 9b - 27
5b - 9b = -27 + 3
-4b = -24
b = -24/-4
b = 6
Her son, Bob, is 6 years old
To find Agatha's age, substitute the value of b to the first equation
a = 5b
a = 5 × 6
a = 30
Agatha is 30 years old
