Explanation:
A = P (1 + r)^n
where A is the final amount,
P is the initial amount,
r is the rate of change per cycle,
and n is the number of cycles.
The rate of change is -20% per 10 minutes. The initial amount is 550 grams.
A = 550 (1 − 0.20)^(t/10)
A = 550 (0.8)^(t/10)
After 55 minutes, there is approximately 161 grams of salt.