The next step is to find out the areas of the three kinds of pizzas respectively, and compare 6 +9 and 12 which is larger. The area of a circle will always be calculated, so I won't say it. It's not cost-effective to work out.
2.C=πd, when the radius increases by 2CM, it is C=π(d+4)=πd+4π, that is, the circumference increases by 4π.
Same area: S=πR? When the radius increases by 2CM, it is S=π(R+2)? =πR？ +4πR+4, which means an increase of 4πR+4.
This kind of problem can't have actual numbers, usually algebra.
3, c is 4 points, there is no process. . . infer
4, set the original x meters
3/4X*2/3* 1/2= 12
X=48 meters
And Baidu, which I don't understand.