What is the length of segment a’b’?

What percent of 18 is 24? and plz explain thx.

Ur environment is very sensitive to the amount of ozone in the upper atmosphere. the level of ozone normally found is 4.04.0 parts/million (ppm). a researcher believes that the current ozone level is not at a normal level. the mean of 2525 samples is 4.44.4 ppm with a standard deviation of 0.80.8. assume the population is normally distributed. a level of significance of 0.020.02 will be used. make the decision to reject or fail to reject the null hypothesis. answer tables

Acircle has a radius of 12.6cm what is the exact length of an arc formed by a central angle measuring 120