Pema Dorji and Kesang Choden are two children in a big family. Pema Dorji has thrice as many sisters as he has brothers. Kesang Choden has two less brothers than she has sisters. How many children are there in the family?

Perma Dorji (PD) and Kesan Choden (KC) are children.

If the number of brother PD has is X, the number of sisters she has is 3X

If the number of brothers KC has is 3X, then the number of sisters she has is 3X-2

Explanation:

The total number of children (brothers and sisters) therefore are:

PDs siblings = 3X+X plus

KCs siblings = 3X2

= 3X+X +3X-2

=6x-2

Let's assume that X is 1, therefore the number of siblings equals

6(1)-2

= 4

Don't forget the PD and KC are also children.

Therefore, the total children in the family is equals to 6

Cheers!

1) gene flow

- it is described as the transfer of genes from one population to another population so that frequency of gene is increased.

-a zebra migrates to join a different herd of zebras.

2) natural selection

- a mechanism of evolutionary change in which individuals with advantageous traits survive and reproduce whereas the others ( those that can not adapt) eliminate from the population.

-competition for sunlight leads to taller trees.

3) mutation

- permanent change in the nucleotide sequence of dna ( genetic material) that could have harmful or useful consequences.

-the dna of a snake changes to make its venom stronger.

4) genetic drift - it is a random phenomenon ( that occurs by chance such as fire) that results in change in the gene frequency in a small population.    

-a grassfire randomly sweeps through a population of buffalo and kills most of the animals.

explanation:

biology is the study of life. it is the study of living organism.