Use PEMDAS, the answer that I got is 19.
Use pythagoras theorem to find height. you get, h=4. so volume ,

u get,v=
The number is 142
you first make an equation ;
86+x=2x-56
Add 56 to both sides
142+x=2x
Subtract x from both sides
142=x
Answer:
By comparison of the sides.
Step-by-step explanation:
If triangles are similar, that means their angles are equal and sides are proportional.
If you already have a proportion of two corresponding sides between triangles, then use that proportion and set it equal to a side you already know the measurement to. Hopefully that side is corresponding to your missing measurement, and you can then solve it.