Frankie can build a speaker box in 120 minutes. tisha can build a speaker box 40 minutes faster. if they work together, how many minutes does it take them to build the speaker box? show work or a picture, i am so confused

The first thing you should know is how long it takes each one to build a box.
 We have then:
 Frankie = 120minutes
 Tisha = 120-40 = 80minutes
 Then, we take the average:
 (120 + 80) / (2) = (200) / (2) = 100 minutes.
 answer
 It takes them to build the speaker box 100 minutes.

The answer is part a: use

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