9514 1404 393
Answer:
40 minutes
Explanation:
The lines are graphed. The point of intersection (A) is where the two sign makers will have made the same number of signs in the same number of minutes. The answer to the question is the x-coordinate of that point, 40 minutes.
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The equation you want to solve is the one that sets Kiran's y-value equal to Lin's y-value
y = y
1/2x +5 = 1/4x +15
1/4x +5 = 15 . . . . . . . . subtract 1/4x
1/4x = 10 . . . . . . . . . . . subtract 5
x = 40 . . . . . . . . . . . . multiply by 4
At 40 minutes, both will have the same number of signs made.
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Alternate solution
Often, you are told to "clear fractions" as a first step in solving equations containing fractions. Here, you would do that by multiplying both sides by 4.
1/2x +5 = 1/4x +15
2x +20 = x + 60 . . . . . multiply by 4
x + 20 = 60 . . . . . . . . . subtract x
x = 40 . . . . . . . . . . . . . subtract 20