25 degrees acute is the answer. Here's how. A triangle totals 180 degrees. The little box in the corner signifies a 90 degree angle. So 180 minus 90 equals 90. Then take that other 65 degrees and subtract it from 90. That leaves you with 25 degrees for x. The equation would be 180- (65+90)= x. Any angle less than 90 degrees is acute.