(1) According to house payment = house unit price × house area, it can be expressed as house payment payable.

(2) When 0≤x≤30, 30 ≤ x ≤ m and x > m, the expressions between Yy and x can be obtained respectively;

(3) When 50≤m≤60 and 45 ≤ m < 50, the conclusions are drawn by discussing and establishing inequality groups respectively.