In a group of students. 20 study Account. 21 Study matematis Study History Study account only 70 study mathematics only and 3 Study mathematics and histork mathematics on How 2202 students we have altogether​

In total there are 50 students.

Step-by-step explanation:

Since in a group of students 20 study account, 21 study mathematics, 18 study history, 7 study account only, 10 study mathematics only, 6 study account and mathematics only and 3 study mathematics and history only, to determine how many student are there altogether the following calculation must be performed:

7 + 10 + 6 + 3 = 26

Account = 20 - 7 - 6 = 7

Mathematics = 21 - 10 - 6 - 3 = 2

History = 18 - 3 = 15

26 + 7 + 2 + 15 = X

50 = X

Therefore, in total there are 50 students.

step-by-step explanation: a reaction is first order. if the initial reactant concentration is 0.0200 m, and 25.0 days later the concentration is 6.25 x 10-4 m, then its half-life is: