{у₃ + у₇ = 180
{5y₇ = y₃
{у₃ = 180 − y₇
→ {5y₇ = 180 − y₇
5y₇ + y₇ = 180
6y₇ = 180
y₇ = 180÷6
y₇ = 30°
→ y₃ = 5 × 30° = 150°
ответ: y₃ = 150°; y₇ = 30°.
{у₃ + у₇ = 180
{5y₇ = y₃
{у₃ = 180 − y₇
{5y₇ = y₃
→ {5y₇ = 180 − y₇
5y₇ + y₇ = 180
6y₇ = 180
y₇ = 180÷6
y₇ = 30°
→ y₃ = 5 × 30° = 150°
ответ: y₃ = 150°; y₇ = 30°.