Answer:
Step-by-step explanation:
We can solve this using the relationship between the angles together with the angle sum theorem. Let s represent the measure of the smallest angle. Then the middle angle is 4s, and the largest angle is (4s +s). The angle sum theorem tells us the sum of angles in a triangle is 180°.
 smallest + middle + largest = 180°
 s +(4s) +(4s +s) = 180°
 10s = 180° . . . . . . . . . . . simplify
 s = 18° . . . . . . . . . divide by 10
 4s = 72° . . . . . . find the middle angle
 4s +s = 72° +18° = 90° . . . . . find the largest angle
The smallest, largest, and middle angles are 18°, 90°, and 72°, respectively.