The key on a pictograph tells what each picture stands for.
Here is your answer and result
Have a nice day
See attachment for solution.
What exactly do you need help with?!
I honestly don’t know. But the square in the bottom of the triangles indicate that it is a right triangle equaling 90 degrees. You can try using that along with other knowledge of right triangles you have. Could you possibly use Pythagorean theorem also?