It’s a triangle 
 s
r t
rs= 2x+10 and st= x-4 
the sides are equal so equal them together then solve
2x+10=x-4
 + 4 +4
2x+14=x
you got x alone so x=2x+14
now you plug in 2x+14 in for the x in rs and st
rs= 2(2x+14)+10
 4x+28+10
 4x+38
st= (2x+14)-4
 2x+14-4
 2x-10
        
             
        
        
        
Answer:
It is an expression
Step-by-step explanation:
An equation needs to have an equal sign in it and 18-35 doesn't  have an equal sign
Hope this helps!! :)