The decrease of the decimal rate -1.05 mm/year can be rounded to -1. You don’t need to round 2.48 because you’re multiplying by -1. Since -1.05 is negative and rounded to a greater value, the estimate could be adjusted to a slightly lesser value, maybe -2.5 or -2.6.
Round 1.05 mm to the nearest whole number the result is -1.1 then round 2.48 which the result will be equal to 3. The total variation in water level is -3.3
because the total rainfall in March was 3.6 inches and if the total rainfall in April was 1.4 times as much then you would take the total rainfall in March which was 3.6 inches and multiply that by 1.4 because it says the amount in April was 1.4 times as much.