This question requires the use of basic trigonometry.
In this problem, we know one of the sides and two of the angles.
Since one of the angles is 45 degrees and the sum of all internal angles of a triangle is 180 degrees, the other angle can only be 45 degrees, making this an isosceles triangle - that is, the length of the other leg, x, is also 7.
You could use the soh cah toa mnemonic to figure it out, but here just using the a^2 + b^2 = c^2 should be sufficient since we know both legs of the triangle.
7^2 + 7^2 = 98, and the square root of 98 gives you about 9.8995, which sounds about right for this situation.
