Let’s form an equation:
a°+c°+60°=360°
We know this because the sum of all three angles form a circle, which has a measure of 360.°
Now, let’s solve for a°+c°
Subtract 60° from both sides.
a°+c°=360-60
a°+c°=300
We subtracted 60 from 360° because we want to take a “piece” of the angle away to find out the sum of a°+c.° It’s like taking away a sector (section of the area) away from a circle.