answer is 25Step-by-step explanation:for something like this you need to use the law of sins. First identify all the angles. There is a 90 degree angle and a 59 degree angle and those are clear. the missing angle is = 59 + 90 = 149 since a triangle has 180 degrees in total you say 180 - 149 = 31. the missing angle is 31 degrees. so we give the angles names. angle with 59 degrees will be angle A, 90 will be B and 31 will be C. So now we just give the sides names. let's replace that x with an a since it's across angle A. the side along angle B will be named b and the side along angle C will be named c. so you say:Sin A/ a (sin A over a) = Sin B/b = Sin C/cSin A is what we are looking for so we say 59 degrees over/ x = sin 31 degrees/ 13 (we leave out the 90 degrees since we don't know the side and also we are not interested in it) now we do cross multiplying. say x ×sin 31 degrees = 13× sin 59now divide these by sin 31x = 13 × sin 59 ÷ 31 = 25