## anonymous 5 years ago 20/r + 12/r-4 = 4

$$\frac{20(r-4)}{r(r-4)}+\frac{12r}{r(r-4)}=4$$ $$\frac{32r-80}{r(r-4)}=4$$ $$32r-80=4r(r-4)$$ $$32r-80=4r^2-16r$$ $$8r-20=r^2-4r$$ $$r^2-12r+20=0$$ $$(r-2)(r-10)=0$$ $$=2$$ or $$r=10$$.