488 CHAPTER 7 Rational Expressions Solve the following. See Example 5. 17. Three times the reciprocal of a number equals 9 times the reciprocal of 6. Find the number 18. Twelve divided by the sum of r and 2 equals the quotient of 4 and the difference of x and 2. Find r. 19. If twice a number added to 3 is divided by the number plus 1, the result is three halves. Find the number, 20. A number added to the product of 6 and the reciprocal of the number equals -5. Find the number. See Example 6. 21. Smith Engineering found that an experienced surveyor surveys a roadbed in 4 hours. An apprentice surveyor needs 5 hours to survey the same stretch of road. If the two work together. find how long it takes them to complete the job. 22. An experienced bricklayer constructs a small wall in 3 hours The apprentice completes the job in 6 hours. Find how long it takes if they work together. 23. In 2 minutes, a conveyor belt moves 300 pounds of recyclable aluminum from the delivery truck to as small- er belt moves the same quantity of cans the same distance in 6 minutes. If both belts are used, find how long it takes to move the cans to the storage area 24. Find how long it takes the conveyor described Exercise 23 to move 1200 pounds of 1200 pounds as as four 300-pound jobs.) 35 See Example 7. 25. A jogger begins her workout by jogging the tance of 12 miles. She then jogs home 36 along a different but