Answer: √35
Explanation:
If two triangles are similar, then that means the ratios of the sides within each triangle will equal each other. Knowing this and that these triangles are similar, we can set the ratio of the known side and the unknown side of each triangle equal to each other.
Doing this, we get the equation
. Notice that 5 is in the numerator while 7 is in the denominator. It could be flipped, but what's important is that they are not both in the numerator or denominator. We know they should not be as in the triangle on the right, 5 is the shorter non-hypotenuse side, whereas on the left, the 7 is the longest non-hypotenuse side, so they do not correspond to the same side.
From this equation, we can just solve for x. Solving for x by cross multiplying gives the answer
.