Ok so firstly, you need to remember that when a radius is touching a tangent, the angle is always equal to 90°. So x + 57° = 90°. That means your angle is 33°. You have drawn a right angle which is correct so the left triangle's angle is 90° - 33° = 57°. Now because both sides of the triangle is radius, that means c and 57° are equal. That means c = 57°.
The question is asking how many ounces of silver are in the bar. We know that 93% of the bar is silver. The bar is 8.15 ounces. This means we need to find 93% of 8.15. Let's set up an equation.