Answer:
a = 
Step-by-step explanation:
I think your question is missed of key information, allow me to add in and hope it will fit the original one.:
<em>Suppose ABC is a right triangle with sides a, b, and c and right angle at C. Find the unknown side length using the Pythagorean theorem and then find the values of the six trigonometric functions for angle B. when b=3 and c=4</em>.
My answer:
We will Pythagoras theorem, which states that the sum of squares of two legs of a right triangle is equal to the square of the hypotenuse of right triangle. Because the question says that ABC is a right triangle.

Given that: b=3 and c=4

so a =
We know that tangent relates opposite side of a right triangle with adjacent side.

Please have a look at the attached photos.
The first one is 5c√10c/3d^3
The answer is: A, 5c√10c/3d^3
Hope this helps! :)
Answer:
25/4 or 6 1/4
Step-by-step explanation:
15 x 5/12 = 5 x 5/4 = 25/4