Problem 1.
The initial sample of deer was 70, and all were tagged. The second event captured 30 and found 7 out of them tagged. Therefore, if we consider that 7 out of 30 was the ratio that represents the proportion of tagged to total, then we can write the following proportion to estimate the number(X) of deer in the population:
7 / 30 = 70 / X
where X can be solve by cross multiplying:
X = 70 * 30 / 7 = 300 deer.
Problem 2.
34% of 785 students ride theit bicycles to school, That is (recalling that 34% is written as 0.34 in decimal form):
0.34 * 785 = 266.9 so about 267 students ride their bicycles to school