Answer: 129,600kg/day
In this question, you are given the river flow (30m3/s) and the salt concentration. Then to determine the amount of salt carried, you simply need to multiply the flow with concentration. Be careful because the unit in this question is different and need to be converted. The equation would be:
Salt = river flow x salt concentration
Salt = 30m3/s x 1000L/m3 x 50mg/L = 1,500,000mg/second
Then convert it into kg/day
Salt= 1,500,000mg/second x 10^-6 kg/mg x (3600 second/hour) x (24 hour/day)= 129,600kg/day