A triangle is always 180 degrees
So, the right angle is 90 degrees and the 7 cm and 12cm. One angle is 90 degrees, so it would be 180 - 90 = 90. Both of the angles are acute = less than 90 degrees. X = less than the other angle. you also need a protector to measure the remaining angles. The bigger angle would be the other one while the less angle would be x.