65°+(3x-10)°+(2x)°=180°
(3x-10)°+(2x)°=180°-65°
(3x-10)°+(2x)°=115°
3x-10+2x=115°
5x-10=115
5x=115+10
5x=125
x=125/5
x=25
so if x=5 then we just replace the x in the formulas
(3x-10)=3×25-10=75-10=65°
So B=65°
(2x)°=2×25=50°
And C=50°
A+B+C=65°+65°+50°=180