Answer:
x ≈ 2.65(nearest hundredth)
Explanation:
Base on your question the triangle is a right angle triangle. This means the triangle should obey the Pythagoras theorem.
Pythagoras theorem says
c² = a² + b²
where
c = hypotenuse of the triangle
a and b are called the legs of the triangle.
The hypotenuse is the longest side of the triangle.
Recall your question says the unknown side x is one of the legs of the triangle. That means the other legs will definitely be 3 since the hypotenuse should be the longest side of the triangle which is 4.
Using Pythagoras theorem
4² = 3² + x²
16 - 9 = x²
7 = x²
square root both sides
x = √7
x = 2.64575131106
x ≈ 2.65(nearest hundredth)