Jill and Sabrina can write a lab report together in $6$ hours. If all people work at the same rate, how many hours would it take to write a lab report if Kelly joins Jill and Sabrina?

Step-by-step explanation:

Let jill, sabrina and kelly be x, y and z respectively.

xy = $6/hour

Assume x = y = z = c, that is they all work at the same rate.

Therefore, if x or y worked individually,

Rate of c = $6 × 2

= $12/hour

If kelly joins,

xyz = 3 × c

= $12/3

= $4/hour

Therefore if kelly joins, the rate will be $4/hour.

first, we define the variables:

x: number of years after 1950

f (x): amount of vinyl sold.

then, with the variables defined, we have:

68594 vinyl records were sold in 1958 > f (8) = 68594

91299 vinyl records were sold in 1961 > f (11) = 91299

38720 vinyl records were sold in 1952 > f (2) = 38720

161743 vinyl records were sold in 1967 > f (17) = 161743

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step-by-step explanation: