= & gt
Deduct X yuan every month, which is equivalent to deposit X yuan in the bank, with a monthly interest of 0.005, and pay it back together when it expires;
X yuan repaid in the first month can increase interest for 239 months, and then decrease in turn.
= & gt
300000*( 1.005)^240
=x( 1.005)^239+x( 1.005)^238+……+x( 1.005)+x
=x*( 1.005^240- 1)/0.005
=2 149.29