Assuming that the total loan amount is P (principal) and the monthly repayment amount is set to M, it is a common calculation method to calculate the monthly repayment amount by using the equal principal and interest repayment method. The formula of monthly contribution m is: m = p× [r/(1-(1+r) (-n)], where r is the monthly interest rate (annual interest rate/12) and n is the total number of months (number of years×12). From the subject conditions, we can know that P=760000, the annual interest rate is unknown, and the loan period is 30 years, which is calculated by substituting into the formula. The calculation result is: 4079.84 yuan. So, you need to pay back 4079.84 yuan every month.