idk what happened to my answer, but I meant 3≤x≤7
anyway, for the second part of the problem, the angle opposite of x will be acute only if 32+52>x2→√34>x. For integer values, that means that it must be smaller or equal to 5.
So that means that if x is 3, 4, or 5, it will make the angle opposite of x be acute, but that doesn't mean that the triangle itself is acute. If x = 4, then it will for a 3-4-5 triangle, which is right. That means that only 3 and 5 works, so the answer is 2
By the way, if you want to manually check if a triangle is obtuse or not, and you're given sides x, y, and z, then all of these these inequalities must hold true:
x2+y2>z2y2+z2>x2x2+z2>y2
.