Answer:
∠a= 65°, ∠b= 115°, ∠c= 25°
Step-by-step explanation:
The sum of the angles in a triangle is 180°. This is abbreviated to '∠ sum of ∆'.
∠c +55° +60° +40°= 180° (∠ sum of ∆PQR)
∠c +155°= 180°
∠c= 180° -155°
∠c= 25°
∠a +60° +55°= 180° (∠ sum of ∆PQS)
∠a +115°= 180°
∠a= 180° -115°
∠a= 65°
The sum of the angles on a straight line is 180°. It's abbreviation is 'adj. ∠s on a str. line'.
∠b +∠a= 180° (adj. ∠s on a str. line)
∠b +65°= 180°
∠b= 180° -65°
∠b= 115°
