Can someone PLEASE explain in simple terms which trigonometric ratio to use, like tangent, cosine, or sine, and WHY?

Use law of Cosines or Tangent

Step-by-step explanation:

This is a SAS triangle, where you have have an angle adjacent to two side lengths. But given that it is a right triangle, you can find the hypotenuse by just using the tangent formula. You can find the quantity of any angle by applying tan= opposite side/adjacent side length.

However, lets say you want to find the opposite side, side XZ, you can use the law of cosine which basically states:

c=a^2+b^2﹣2abcos(angle number).  But since it is a right triangle, just use the hypotenuse theorem which states: C^2 = A^2 + B^2

The answer for XZ would thus be: squareroot of 136 or 2(34)^1/2.

Hope this helps :)