The value for the missing term is -175.
ABC
MIT
MEL
are right triangles
to solve this you can get help from
ThePythagorean Proposition
or use an useful app all in one calculator
To find the surface area of a rectangular prism or cube, you would do height*width*2+height*length*2+length*width*2.
Remember to use SOH CAH TOA. Very simple. I ended up getting 18/17 as my answer