Answer:
x = 5
Explanation:
I see no diagram.
I assume, this is a right-angled triangle, and x is supposed to be the Hypotenuse (the side opposite of the 90 degree angle).
then Pythagoras
c² = a² + b²
where c is the Hypotenuse,
looks like this for our case :
x² = 3² + 4² = 9 + 16 = 25
x = 5
just in case, if x is not the Hypotenuse, then the only other valid option for a right-angled triangle is for the longer one of the other sides to be the Hypotenuse.
then Pythagoras would look like this
4² = 3² + x²
16 = 9 + x²
7 = x²
x = sqare root of 7 = 2.65