Answer: 19
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Step-by-step explanation:
The tickmarks tell us which segments are congruent (i.e. the same length).
We can see that:
JM = MK
because of the single tickmarks. Since these segments are the same length, we know that M is the midpoint of segment JK. The midpoint divides a segment into two equal pieces.
Similarly, N is the midpoint of segment LK.
Midpoints M and N join up to form midsegment MN.
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Rules:
- The midsegment of a triangle is parallel to the side it doesn't go through.
- The midsegment is half as long compared to the parallel side.
Rule 2 is what we'll focus on.
MN is half as long as the side JL.
This can be rephrased to: "JL is twice as long as MN".
So,
JL = 2*(MN)
8x-18 = 2*(2x+5)
8x-18 = 4x+10
8x-4x = 10+18
4x = 28
x = 28/4
x = 7
Then we can determine each segment length:
- MN = 2x+5 = 2*7+5 = 14+5 = 19 is the answer
- JL = 8x-18 = 8*7-18 = 56-18 = 38
Notice that JL = 38 is twice as long compared to MN = 19
Or you could say: JL/MN = 38/19 = 2, which helps verify the answer.