It is c
i hope this helps
3.

4. Cross- multiply
8.

9.

10.

11. Line Segment Additive Property
That would be -0.4, my good sir.
These are similar triangles so proportions hold. the short side to the bottom side proportion must be the same in both triangles. to solve it
25/30 = 35/x. (25+10=35 is the side of the bigger triangle
cross multiply and solve for x
25x=1050
x=1050/25=42