If a large pizza has a radius that is 30% larger

Hello M7MBA.

Let's suposse that the radius of the medium pizza is equal to r. This implies that the radius of the large pizza is r+0.3r=1.3r.

Now, the area of the medium pizza is $$\pi\cdot r^2$$ and the radius of the large pizza is $$\pi\cdot (1.3r)^2=1.69\pi\cdot r^2.$$ Therefore, the difference between them is $$1.69\pi\cdot r^2 - \pi\cdot r^2\ =\ 0.69\pi\cdot r^2.$$ Now, we have to find what percent represents this to the area of the medium pizza.

$$\pi\cdot r^2----------100\%$$ $$0.69\pi\cdot r^2----------x\%$$ Hence $$x=69\%.$$ Thus, the answer is d .