Since one of the angles is 45 degrees and the other one is a right angle, you have an isosceles right triangle, which is a special right triangle. The hypotenuse is the square root of 2 times one of the legs. One of the legs is x. The hypotenuse is 5. Using the information I stated earlier, we know that x√(2) = 5. Now we have an equation we can solve.
x√(2) = 5
Divide both sides by √(2)
x = 5 / √(2)
Simplify
x = (5 √(2) ) / 2
There's your answer.
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