To solve triangles, you first need to establish the labels of the sides. Since you already have 15° for an angle, use that angle to label. The longest side is always the hypotenuse (across from the right angle). The one opposite your angle (5) is the opposite side, and the remaining one (x) is the adjacent.
Now, to find x, you need to set up a ratio involving it and your other given side, the opposite. The correct trig ratio for this is going to be Tangent (
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). Set the Tangent of your angle equal to its ratio.
tan(15) =

Now, get x by itself and solve like a regular equation
x(tan(15)) = 5 Divide by tan(15)
x =
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Plug this into a calculator
x = 18.660
x ≈ 18.7So, the correct answer is
2 .