Question

What is the value of c? units?

Answer 1

You may recognize that ∆WYZ is a 3-4-5 right triangle. Without any work, then
  c = 5

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If you don't remember that a right triangle with legs 3 and 4 has a hypotenuse of 5, you can compute it using the Pythagorean theorem.
  c² = 3² + 4²
  c² = 9 + 16 = 25
  c = √25 = 5

Answer 2

We can use the Pythagorean theorem to find c. This theorem says that a^2 + b^2 = c^2 where a and b are the opposite and adjacent, and c is the hypotenuse. In this case 3 and 4 serve as a and b.

3^2 + 4^2 = c^2      9 + 16 = c^2     25 = c^2     sqrt(25) = c5 = c     So c is 5 units.