Important for :

1

2

B

The sum of opposite angles of a concyclic quadrilateral is 180°.

∴ ∠A + ∠C = 180°

4x + 5y = 180° ...(i)

∠B + ∠D = 180°

7x + y = 180° ...(ii)

By equation (ii) × 5 – (i), we get

31x = 720

x = | 720 |

31 |

From equation (ii),

7x + y = 180°

7 × | 720 | + y = 180° |

31 |

y = 180° – | 5040 | = | 540 |

31 | 31 |

∴ x : y = | 720 | : | 540 | = 4 : 3 |

31 | 31 |

Hence, option B is correct.

3

4

5