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