The base is a square, therefore all the sides of the base are the same. This also means all the triangles have the same area.
10*10 = 100 cm^2 for the base
0.5*10*12 = 60 cm^2 for each triangle
100 + 4(60) = 340 cm^2
Last option is your answer ( 0.00000991)
To simplify that expression you'll join like terms.
8x + 4 - 5
8x - 1
A. 305
b. 900
c. 46
d. 157,019