If Keith is represented by x, and Joe is three less than Keith, Troy is represented by x-3. Then, we know that Joe exercises for twice the amount of time as Troy, we multiply the expression for Joe by two.
We can see that out of all the people that were surveyed, 54% were 10th graders. Since 33% out of all the ones surveyed were 10th graders that chose robotics, the fraction would be 33/54 which is 0.611.
