Răspuns :
fie x masura lui A
mA+mB+mC=180
4x+20=180
4x=160
x=40
mA=40
mB=20
mC=120
mA+mB+mC=180
4x+20=180
4x=160
x=40
mA=40
mB=20
mC=120
m(A) +m(B) +m(C) = 180⁰
↓ ↓
m(A) + 20⁰ + 3m(A) =180⁰
4m(A) = 180⁰ - 20 ⁰
4m(A) =160⁰
m(A) = 160⁰ :4 = 40⁰
↓ ↓
m(A) + 20⁰ + 3m(A) =180⁰
4m(A) = 180⁰ - 20 ⁰
4m(A) =160⁰
m(A) = 160⁰ :4 = 40⁰