v(x)=(2x-3)/(5x+4) is restricted by the denominator. When x=-4/5, t(x)=0 and v(x) is undefinable.
w(x) is similarly undefinable at x=3/2 because s(x)=0; w(x)=(5x+4)/(2x-3).
v(x) and w(x) are otherwise definable for all x. Domain for v(x) is all x<>-4/5 and for w(x) it's all x<>3/2.