could you solve this using u substitution? if so, please do and show all work

A wound is healing in such a way that t days since Sunday the area of the wound has been decreasing at a rate of -3/(t+21 cm per day. If on Monday the area of the wound was 2cm (i) What was the area of the wound on Sunday? (ii) What is the anticipated area of the wound on Thursday if it continues to heal at the same rate? Solution: Let "A" be the are of wound and "t" be the days By integrating the wound on Sunday, we get the area of wound on Monday. Rate of change (dA/dt) = -3/(t+21 cm/ per day [dA= -3 [(t+2)2 dt A = 3 (t+21 +0 A = 3/(t+2)+c (1) When A = 2, t = 1