x - any unit in degrees
The ratio 7 : 8, therefeor the measures of the angles are 7x and 8x.
We know: the sum of those angles is 180°
Therefore we have the equation
7x + 8x = 180
15x = 180 |:15
x = 12
The smaller angle is 7x.
Your answer is 7 · 12° = 84°
