7. Find the number of vertices of a polyhedron
having 10 faces and 12 edges

4

Step-by-step explanation:

Using Euler's rule for polyhedra

F + V - E = 2 ( F - faces, V- vertices, E- edges )

10 + V - 12 = 2

V - 2 = 2 ( add 2 to both sides )

V = 4

trapezoid

step-by-step explanation:

first i plotted all my points on a grid graph

i made sure all of them were in the correct quadrant

then i saw it was a trapezoid or a quadrilateral